pinctrl: cy8c95x0: Lock register accesses in cy8c95x0_set_mux()

It seems that cy8c95x0_set_mux() missed serialization of IO access.
And its implementation looks half-baked. Add locking to the function.

Fixes: e6cbbe42 ("pinctrl: Add Cypress cy8c95x0 support")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220916205450.86278-1-andriy.shevchenko@linux.intel.com


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