gpio: 104-idi-48: Migrate to the regmap-irq API

The regmap API supports IO port accessors so we can take advantage of
regmap abstractions rather than handling access to the device registers
directly in the driver.

For the 104-idi-48, we get an IRQ register with some status information
and basic masking, but it's broken down by banks rather than individual
GPIO. There are six banks (8 GPIO lines each) that correspond to the
lower six bits of the IRQ register (bits 0-5):

    Base Address + 7 (Read): IRQ Status Register/IRQ Clear
        Bit 0-5: Respective Bank IRQ Statuses
        Bit 6: IRQ Status (Active Low)
        Bit 7: IRQ Enable Status
    Base Address + 7 (Write): IRQ Enable/Disable
        Bit 0-5: Respective Bank IRQ Enable/Disable
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/Kconfig

@@ -872,6 +872,8 @@ config GPIO_104_IDI_48
 	tristate "ACCES 104-IDI-48 GPIO support"
 	depends on PC104
 	select ISA_BUS_API
+	select REGMAP_MMIO
+	select REGMAP_IRQ
 	select GPIOLIB_IRQCHIP
 	select GPIO_I8255
 	help