vidc: Move metadata shared input mem to firmware heap.

Metadata shared input is used to communicate between
the video code and video driver, hence make this buffer
as uncached and allocate it from firmware heap.

Change-Id: Ib1f4005bae1778f68d228bd3c798457c7c15d83d
Signed-off-by: Deepak Kotur <dkotur@codeaurora.org>