clk: qcom: gdsc: add collapse-bit helper

Add a helper for updating the SW_COLLAPSE bit during initialisation and
state updates.

Note that the update during initialisation was relying on the
SW_COLLAPSE bit not having been set earlier rather than passing in zero
explicitly to clear the collapse vote.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220520100948.19622-2-johan+linaro@kernel.org