pinctrl: qcom: lpass-lpi: fix concurrent register updates

The Qualcomm LPASS LPI pin controller driver uses one lock for guarding
Read-Modify-Write code for slew rate registers.  However the pin
configuration and muxing registers have exactly the same RMW code but
are not protected.

Pin controller framework does not provide locking here, thus it is
possible to trigger simultaneous change of pin configuration registers
resulting in non-atomic changes.

Protect from concurrent access by re-using the same lock used to cover
the slew rate register.  Using the same lock instead of adding second
one will make more sense, once we add support for newer Qualcomm SoC,
where slew rate is configured in the same register as pin
configuration/muxing.

Fixes: 6e261d10

 ("pinctrl: qcom: Add sm8250 lpass lpi pinctrl driver")
Cc: stable@vger.kernel.org
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231013145705.219954-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>