msm: vidc: Change in input buffer size calculation

Right now, input buffer size is calculated based on
maximum supported height and width returned from FW.
These values are not true representation as they are
calculated for rotation usecase. Driver needs to use
max MB supported from FW. This change fixes the same.

CRs-Fixed: 599818
Signed-off-by: Manikanta Sivapala <msivap@codeaurora.org>

Conflicts:
	drivers/media/platform/msm/vidc/msm_vdec.c

Change-Id: Ibd73490c9b42bb88d68b835941ebe764a15aaaf9