Add clkdev support for the ep93xx_keypad driver.

A matrix keypad driver for the ep93xx just got merged via the
input subsystem group.  For this driver to work the keypad clock
needs to be added to the ep93xx clkdev support.  In order to
accomplish this the following changes are implemented:

  1) Move the EP93XX_EXT_*_RATE defines to mach/include/hardware.h.
  2) Add EP93XX_KEYTCHCLK_DIV{4/16} for the keypad driver.
  3) Add support for programmable clocks (set_rate() callback).
  4) Add clk_keypad for the keypad driver.
  5) tab indent the clk_lookup table for easier reading.
  6) Add the set_rate() callback to program the keypad clock.
     This callback is generalized since the ADC clock (touchscreen)
     can use the same callback.
  7) Use the ep93xx_syscon_swlocked_write() core function for updating
     the software locked register.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>