drm/msm/sde: update 1.8G BW vote during cont-splash

During power enable for the first time, data bus vote is
0 ab and 400 Mbp ib. In few scenarios this reduction in vote
during continuous splash for few ms is causing underrun.
Update 1.8G ab and ib bandwidth vote at first power enable
to avoid underrun on video mode in continuous splash usecase.

Change-Id: Ida604687329d902c7063f8500277b649fa831817
Signed-off-by: Raviteja Tamatam <travitej@codeaurora.org>