gpio/ep93xx: convert to platform_driver and use basic_mmio_gpio library

This converts the gpio-ep93xx driver into a platform_driver and uses
the basic_mmio_gpio library.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index b84666a..9f06e63 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -87,6 +87,7 @@
 config GPIO_EP93XX
 	def_bool y
 	depends on ARCH_EP93XX
+	select GPIO_GENERIC
 
 config GPIO_EXYNOS4
 	def_bool y