gpio/mxs: Change gpio-mxs into an upstanding gpio driver

The patch makes necessary changes on gpio-mxs as below to turn it
into an upstanding gpio driver.

 * Clean up the gpio port definition stuff

 * Use readl/writel to replace mach-specific accessors
   __raw_readl/__raw_writel

 * Change mxs_gpio_init into mxs_gpio_probe function

And it then migrates mach-mxs to the updated driver by adding
corresponding platform devices.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/arch/arm/mach-mxs/devices.c b/arch/arm/mach-mxs/devices.c
index cfdb6b2..fe3e847 100644
--- a/arch/arm/mach-mxs/devices.c
+++ b/arch/arm/mach-mxs/devices.c
@@ -88,3 +88,14 @@
 
 	return amba_device_register(adev, &iomem_resource);
 }
+
+struct device mxs_apbh_bus = {
+	.init_name	= "mxs_apbh",
+	.parent         = &platform_bus,
+};
+
+static int __init mxs_device_init(void)
+{
+	return device_register(&mxs_apbh_bus);
+}
+core_initcall(mxs_device_init);