msm: vidc: Update buffer size calculation

Simplify buffer size calculation for both enc/dec for
input/output. Calculate encoder extradata sizes correctly.
Also, for VP9 thumbnail publish correct output buffer
counts.

CRs-Fixed: 2368458
Change-Id: I0fbb7e5237dd07971bfd6a6ecd272eb4a8b20b32
Signed-off-by: Vaibhav Deshu Venkatesh <vdeshuve@codeaurora.org>