msm: vidc: consider max of dpb-opb resolutions to kick-in DCVS

In case of down scalar enabled, opb resolution is considered
to calculate macro blocks per frame.
Calculating macro blocks per frame based on max of dpb-opb resolutions.

Change-Id: I5149f078349bce8341ebc5e410b5247f028d8452
Signed-off-by: Srinu Gorle <sgorle@codeaurora.org>
CRs-Fixed: 970253