msm: vidc: Propagate FBD buffer offset

The offset is used to know the position of the valid data. In the past
this was not use for any codec but is essential for VPX/VP8 encoder.

Change-Id: Id0c5cef74f3ec80a0c41646a3e95d50889932f18
Signed-off-by: Jorge Solano Altamirano <jsolano@codeaurora.org>