msm: vidc: Consolidate get controls in one place

Get control is currently implemented separately for
encoder and decoder. This change replaces indivdual get
controls with a common one.

CRs-Fixed: 2368458
Change-Id: Ia116bea60f92a8e4b7c87a343180eb7d98b11da0
Signed-off-by: Vaibhav Deshu Venkatesh <vdeshuve@codeaurora.org>