gpio: 104-dio-48e: 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-dio-48e we have the following IRQ registers (0xB and 0xF):

    Base Address +B (Write): Enable Interrupt
    Base Address +B (Read): Disable Interrupt
    Base Address +F (Read/Write): Clear Interrupt

Any write to 0xB will enable interrupts, while any read will disable
interrupts. Interrupts are cleared by a write to 0xF. There's no IRQ
status register, so software has to assume that if an interrupt is
raised then it was for the 104-DIO-48E device.
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

@@ -845,6 +845,8 @@ config GPIO_104_DIO_48E
 	tristate "ACCES 104-DIO-48E GPIO support"
 	depends on PC104
 	select ISA_BUS_API
+	select REGMAP_MMIO
+	select REGMAP_IRQ
 	select GPIOLIB_IRQCHIP
 	select GPIO_I8255
 	help