Convert CONFIG_BCM2835_GPIO to Kconfig

This converts the following to Kconfig:
   CONFIG_BCM2835_GPIO

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index c3f1109..a55e368 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -84,6 +84,10 @@
 	  Select this to enable PIO for Altera devices. Please find
 	  details on the "Embedded Peripherals IP User Guide" of Altera.
 
+config BCM2835_GPIO
+	bool "BCM2835 GPIO driver"
+	depends on DM_GPIO
+
 config BCM6345_GPIO
 	bool "BCM6345 GPIO driver"
 	depends on DM_GPIO && (ARCH_BMIPS || ARCH_BCM68360 || \