This converts the GPIO-based I2C-driver to using GPIO
descriptors instead of the old global numberspace-based
GPIO interface. We:

- Convert the driver to unconditionally grab two GPIOs
  from the device by index 0 (SDA) and 1 (SCL) which
  will work fine with device tree and descriptor tables.
  The existing device trees will continue to work just
  like before, but without any roundtrip through the
  global numberspace.

- Brutally convert all boardfiles still passing global
  GPIOs by registering descriptor tables associated with
  the devices instead so this driver does not need to keep
  supporting passing any GPIO numbers as platform data.

There is no stepwise approach as elegant as this, I
strongly prefer this big hammer over any antsteps for this
conversion. This way the old GPIO numbers go away and
NEVER COME BACK.

Special conversion for the different boards utilizing
I2C-GPIO:

- EP93xx (arch/arm/mach-ep93xx): pretty straight forward as
  all boards were using the same two GPIO lines, just define
  these two in a lookup table for "i2c-gpio" and register
  these along with the device. None of them define any
  other platform data so just pass NULL as platform data.
  This platform selects GPIOLIB so all should be smooth.
  The pins appear on a gpiochip for bank "G" as pins 1 (SDA)
  and 0 (SCL).

- IXP4 (arch/arm/mach-ixp4): descriptor tables have to
  be registered for each board separately. They all use
  "IXP4XX_GPIO_CHIP" so it is pretty straight forward.
  Most board define no other platform data than SCL/SDA
  so they can drop the #include of <linux/i2c-gpio.h> and
  assign NULL to platform data.

  The "goramo_mlr" (Goramo Multilink Router) board is a bit
  worrisome: it implements its own I2C bit-banging in the
  board file, and optionally registers an I2C serial port,
  but claims the same GPIO lines for itself in the board file.
  This is not going to work: there will be competition for the
  GPIO lines, so delete the optional extra I2C bus instead, no
  I2C devices are registered on it anyway, there are just hints
  that it may contain an EEPROM that may be accessed from
  userspace. This needs to be fixed up properly by the serial
  clock using I2C emulation so drop a note in the code.

- KS8695 board acs5k (arch/arm/mach-ks8695/board-acs5.c)
  has some platform data in addition to the pins so it needs to
  be kept around sans GPIO lines. Its GPIO chip is named
  "KS8695" and the arch selects GPIOLIB.

- PXA boards (arch/arm/mach-pxa/*) use some of the platform
  data so it needs to be preserved here. The viper board even
  registers two GPIO I2Cs. The gpiochip is named "gpio-pxa" and
  the arch selects GPIOLIB.

- SA1100 Simpad (arch/arm/mach-sa1100/simpad.c) defines a GPIO
  I2C bus, and the arch selects GPIOLIB.

- Blackfin boards (arch/blackfin/bf533 etc) for these I assume
  their I2C GPIOs refer to the local gpiochip defined in
  arch/blackfin/kernel/bfin_gpio.c names "BFIN-GPIO".
  The arch selects GPIOLIB. The boards get spiked with
  IF_ENABLED(I2C_GPIO) but that is a side effect of it
  being like that already (I would just have Kconfig select
  I2C_GPIO and get rid of them all.) I also delete any
  platform data set to 0 as it will get that value anyway
  from static declartions of platform data.

- The MIPS selects GPIOLIB and the Alchemy machine is using
  two local GPIO chips, one of them has a GPIO I2C. We need
  to adjust the local offset from the global number space here.
  The ATH79 has a proper GPIO driver in drivers/gpio/gpio-ath79.c
  and AFAICT the chip is named "ath79-gpio" and the PB44
  PCF857x expander spawns from this on GPIO 1 and 0. The latter
  board only use the platform data to specify pins so it can be
  cut altogether after this.

- The MFD Silicon Motion SM501 is a special case. It dynamically
  spawns an I2C bus off the MFD using sm501_create_subdev().
  We use an approach to dynamically create a machine descriptor
  table and attach this to the "SM501-LOW" or "SM501-HIGH"
  gpiochip. We use chip-local offsets to grab the right lines.
  We can get rid of two local static inline helpers as part
  of this refactoring.

Cc: Steven Miao <realmz6@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Heiko Schocher <hs@denx.de>
Acked-by: Wu, Aaron <Aaron.Wu@analog.com>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>