msm: vidc: Vote for buses immediately after allocing and freeing ocmem

Currently, ocmem bus is voted for accidently when vote_buses is called
as part of a qbuf or a dqbuf. However, this relies on some other driver
helpfully voting for the bus so that Venus isn't blocked on processing a
frame.

The Venus driver needs to vote the ocmem bus well before Venus does
anything with ocmem, as such vote immediately after allocating ocmem.

Change-Id: I34d5a48c721d6c55d351fa9a7cf702c5127ea116
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>