pinctrl: core: Remove unused members from struct group_desc

All drivers are converted to use embedded struct pingroup.
Remove unused members from struct group_desc.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20231211190321.307330-14-andriy.shevchenko@linux.intel.com


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