gpio: fixes for gpio-hog support

recently added gpio hog patch was "in discussion"
state with Simon Glass. This patch now adds most
of comments from Simon Glass.

Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 800584f..7d9c97f 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -14,7 +14,7 @@
 	  particular GPIOs that they provide. The uclass interface
 	  is defined in include/asm-generic/gpio.h.
 
-config DM_GPIO_HOG
+config GPIO_HOG
 	bool "Enable GPIO hog support"
 	depends on DM_GPIO
 	default n