pinctrl: Enable "power-source" to be extracted from DT files

Add "power-source" property to generic options used for DT parsing files.
This  enables drivers, which use generic pin configurations, to get the
value passed to this property.
Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt

@@ -156,6 +156,7 @@ input-disable		- disable input on pin (no effect on output)
 input-schmitt-enable	- enable schmitt-trigger mode
 input-schmitt-disable	- disable schmitt-trigger mode
 input-debounce		- debounce mode with debound time X
+power-source		- select between different power supplies
 low-power-enable	- enable low power mode
 low-power-disable	- disable low power mode
 output-low		- set the pin to output mode with low level

drivers/pinctrl/pinconf-generic.c

@@ -166,6 +166,7 @@ static struct pinconf_generic_dt_params dt_params[] = {
 	{ "input-schmitt-enable", PIN_CONFIG_INPUT_SCHMITT_ENABLE, 1 },
 	{ "input-schmitt-disable", PIN_CONFIG_INPUT_SCHMITT_ENABLE, 0 },
 	{ "input-debounce", PIN_CONFIG_INPUT_DEBOUNCE, 0 },
+	{ "power-source", PIN_CONFIG_POWER_SOURCE, 0 },
 	{ "low-power-enable", PIN_CONFIG_LOW_POWER_MODE, 1 },
 	{ "low-power-disable", PIN_CONFIG_LOW_POWER_MODE, 0 },
 	{ "output-low", PIN_CONFIG_OUTPUT, 0, },