pinctrl: pinmux: Add a convenient define PINCTRL_FUNCTION_DESC()

Add PINCTRL_FUNCTION_DESC() macro for inline use.

While at it, fix adjective form in the comment of PINCTRL_GROUP_DESC().

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20240530085745.1539925-6-andy.shevchenko@gmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>