basic_mmio_gpio: split into a gpio library and platform device

Allow GPIO_BASIC_MMIO_CORE to be used to provide an accessor library
for implementing GPIO drivers whilst abstracting the register access
detail.  Based on a patch from Anton Vorontsov[1] and adapted to allow
bgpio_chip to be embedded in another structure.

Changes since v1:
	- Register the gpio_chip in the platform device probe

1. https://lkml.org/lkml/2011/4/19/401

Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/gpio/Kconfig

@@ -70,8 +70,14 @@ config GPIO_MAX730X
 
 comment "Memory mapped GPIO drivers:"
 
+config GPIO_BASIC_MMIO_CORE
+	tristate
+	help
+	  Provides core functionality for basic memory-mapped GPIO controllers.
+
 config GPIO_BASIC_MMIO
 	tristate "Basic memory-mapped GPIO controllers support"
+	select GPIO_BASIC_MMIO_CORE
 	help
 	  Say yes here to support basic memory-mapped GPIO controllers.
 

drivers/gpio/Makefile

@@ -6,6 +6,7 @@ obj-$(CONFIG_GPIOLIB)		+= gpiolib.o
 
 obj-$(CONFIG_GPIO_ADP5520)	+= adp5520-gpio.o
 obj-$(CONFIG_GPIO_ADP5588)	+= adp5588-gpio.o
+obj-$(CONFIG_GPIO_BASIC_MMIO_CORE)	+= basic_mmio_gpio.o
 obj-$(CONFIG_GPIO_BASIC_MMIO)	+= basic_mmio_gpio.o
 obj-$(CONFIG_GPIO_LANGWELL)	+= langwell_gpio.o
 obj-$(CONFIG_GPIO_MAX730X)	+= max730x.o