pinctrl: amd: Add amd_get_iomux_res function

Presently there is no way to change pinmux configuration run time.
Hence add a function to get IOMUX resource which can be used to
configure IOMUX GPIO pins run time.

Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220601152900.1012813-6-Basavaraj.Natikar@amd.com


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