msm: vidc: Clean-up duplicate code

Similar functionality code is duplicated across decoder and
encoder. Unifying at common place makes it easy to maintain,
less error prone and reduce SLOC.

CRs-Fixed: 2012385
Change-Id: I3e4738c4455fd4427b81bea2ab4d2c5d4ea89f0e
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>