pinctrl: pinmux: Remove unused members from struct function_desc

All drivers are converted to use embedded struct pinfunction.
Remove unused members from struct function_desc.

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20240530085745.1539925-12-andy.shevchenko@gmail.com


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