drm/msm/sde: fix check for regulators under HW control

Fix the check for regulators under HW control by explicitly
checking for GDSC regulators. This will ensure that all other
non-GDSC regulators can be enabled/disabled using the utility
function and therefore prevent unbalanced state change.

CRs-Fixed: 2331331
Change-Id: I8db9b7a398718ac7a4621d0b16e7b6f5d86ff696
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>