pinctrl: core: Embed struct pingroup into struct group_desc

struct group_desc is a particular version of the struct pingroup
with associated opaque data. Start switching pin control core and
drivers to use it explicitly.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20231211190321.307330-5-andriy.shevchenko@linux.intel.com


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