clk: qcom: gdsc-regulator: correct gdsc_disable() success return value

Currently gdsc_disable() can return a value of 1 upon
successfully disabling a GDSC if it has a parent supply.
Correct this so that 0 is always returned on success.

Change-Id: I37ade1bf62b4e8b2f3446b9072674935579d75dd
Signed-off-by: David Collins <collinsd@codeaurora.org>