msm: vidc: Restructure input/output buffer size calculation

Currently buffer size for input/output is calculated in the
corresponding venc and vdec files. Move this to the new
buffer calculations file. Add a new header file to hold
buffer size calculation function/structure declarations.

CRs-Fixed: 2368458
Change-Id: I179d6b827476118a6941902a43a1c274dc47e57d
Signed-off-by: Vaibhav Deshu Venkatesh <vdeshuve@codeaurora.org>