msm: venc: increase output buffer size only for hevc

10 bit support is available only for hevc codec type.
So increase encoder output buffer size(factor - 1.25)
only for hevc.

Change-Id: I49f6bccc074814d8c737f47fd82907a018ac169a
Signed-off-by: Govindaraj Rajagopal <grajagop@codeaurora.org>