pinctrl: pinctrl-cy8c95x0: Fix regcache

The size of the mux stride was off by one, which could result in
invalid pin configuration on the device side or invalid state
readings on the software side.

While on it also update the code and:
- Increase the mux stride size to 16
- Align the virtual muxed regmap range to 16
- Start the regmap window at the selector
- Mark reserved registers as not-readable

Fixes: 8670de9f ("pinctrl: cy8c95x0: Use regmap ranges")
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reported-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://lore.kernel.org/20240902072859.583490-1-patrick.rudolph@9elements.com


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