pinctrl: pinconf-generic: add drive strength parameter

Some pin configurations IP allows to set the current output to the pin.
This patch adds such a parameter to the pinconf-generic mechanism.

This parameter takes as argument the drive strength in mA.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/pinctrl/pinconf-generic.h

@@ -46,6 +46,8 @@
  * @PIN_CONFIG_DRIVE_OPEN_SOURCE: the pin will be driven with open source
  *	(open emitter). Sending this config will enabale open drain mode, the
  *	argument is ignored.
+ * @PIN_CONFIG_DRIVE_STRENGTH: the pin will output the current passed as
+ * 	argument. The argument is in mA.
  * @PIN_CONFIG_INPUT_SCHMITT_DISABLE: disable schmitt-trigger mode on the pin.
  * @PIN_CONFIG_INPUT_SCHMITT: this will configure an input pin to run in
  *	schmitt-trigger mode. If the schmitt-trigger has adjustable hysteresis,
@@ -76,6 +78,7 @@ enum pin_config_param {
 	PIN_CONFIG_DRIVE_PUSH_PULL,
 	PIN_CONFIG_DRIVE_OPEN_DRAIN,
 	PIN_CONFIG_DRIVE_OPEN_SOURCE,
+	PIN_CONFIG_DRIVE_STRENGTH,
 	PIN_CONFIG_INPUT_SCHMITT_DISABLE,
 	PIN_CONFIG_INPUT_SCHMITT,
 	PIN_CONFIG_INPUT_DEBOUNCE,