pinctrl: samsung: support a bus clock

On some Samsung-based SoCs there are separate bus clocks / gates each
for each pinctrl instance. To be able to access each pinctrl instance's
registers, this bus clock needs to be running, otherwise register
access will hang. Google Tensor gs101 is one example for such an
implementation.

Update the driver to handle this optional bus clock:
* handle an optional bus clock from DT
* prepare it during driver probe
* enclose all relevant register accesses with a clock enable & disable

Signed-off-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/r/20240426-samsung-pinctrl-busclock-v3-2-adb8664b8a7e@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>