gpio: add gpio-hog support

add gpio-hog support. GPIO hogging is a mechanism
providing automatic GPIO request and configuration
as part of the gpio-controller's driver probe function.

for more infos see:
doc/device-tree-bindings/gpio/gpio.txt

Signed-off-by: Heiko Schocher <hs@denx.de>
Tested-by: Michal Simek <michal.simek@xilinx.com> (zcu102)
Tested-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index e36a8ab..fa1c997 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -14,6 +14,16 @@
 	  particular GPIOs that they provide. The uclass interface
 	  is defined in include/asm-generic/gpio.h.
 
+config DM_GPIO_HOG
+	bool "Enable GPIO hog support"
+	depends on DM_GPIO
+	default n
+	help
+	  Enable gpio hog support
+	  The GPIO chip may contain GPIO hog definitions. GPIO hogging
+	  is a mechanism providing automatic GPIO request and config-
+	  uration as part of the gpio-controller's driver probe function.
+
 config ALTERA_PIO
 	bool "Altera PIO driver"
 	depends on DM_GPIO