regulator: dt-bindings: qcom,qca6390-pmu: document the swctrl-gpios property

Add support for the swctrl-gpios property which contains the phandle to
the GPIO indicating the clock supply to the BT module.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://patch.msgid.link/20240813185827.154779-3-brgl@bgdev.pl


Signed-off-by: Mark Brown <broonie@kernel.org>