pinctrl: Add PIN_CONFIG_MODE_PWM to enum pin_config_param

It seems that we will have more and more pin controllers that support
PWM function on the (selected) pins. Due to it being a part of pin
controller IP the idea is to have some code that will switch the mode
and attach the corresponding driver, for example, via using it as
a library. Meanwhile, put a corresponding item to the pin_config_param
enumerator.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210412140741.39946-3-andriy.shevchenko@linux.intel.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/pinctrl/pinconf-generic.h

@@ -80,6 +80,7 @@ struct pinctrl_map;
  *	operation, if several modes of operation are supported these can be
  *	passed in the argument on a custom form, else just use argument 1
  *	to indicate low power mode, argument 0 turns low power mode off.
+ * @PIN_CONFIG_MODE_PWM: this will configure the pin for PWM
  * @PIN_CONFIG_OUTPUT_ENABLE: this will enable the pin's output mode
  * 	without driving a value there. For most platforms this reduces to
  * 	enable the output buffers and then let the pin controller current
@@ -125,6 +126,7 @@ enum pin_config_param {
 	PIN_CONFIG_INPUT_SCHMITT,
 	PIN_CONFIG_INPUT_SCHMITT_ENABLE,
 	PIN_CONFIG_MODE_LOW_POWER,
+	PIN_CONFIG_MODE_PWM,
 	PIN_CONFIG_OUTPUT_ENABLE,
 	PIN_CONFIG_OUTPUT,
 	PIN_CONFIG_PERSIST_STATE,