drm/msm/sde: disable vblank ref power on crtc disable

Update vblank reference counts via the exposed sde_crtc_vblank
function, rather than attempting to zero it on the side during
CRTC disable operations. This allows the power voting to be
updated correctly based on the vblank reference count value.

CRs-Fixed: 2037677
Change-Id: I7026a1b239503a2b1d97ad7bb61fbc0a4a38d7ea
Signed-off-by: Clarence Ip <cip@codeaurora.org>