pinctrl: cy8c95x0: Update cache modification

pinctrl: cy8c95x0: Update cache modification

In the previous review cycle the regmap cache update code was
questioned since it seems and odd way of using regmap_update_bits().
Thus update the regmap cache modification code to better explain
what it does and why it's done. This is no functional change, but
it's improving code maintainability.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Link: https://lore.kernel.org/20240626084525.787298-2-patrick.rudolph@9elements.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>