vidc: 1080p : Add support for skip frame in slice delivery mode

Slice delivery mode for H264 encoder will deliver constant number of
output slice buffers for each frame. In case of CBR rate control method,
core will skip frames to maintain the output quality, in which case
driver need to send out the output buffers with data length as zero
for skipped frame output type from the core.

Change-Id: Id81330b28f1f17b97eb2c79c86558bd072b62c4e
CRs-fixed: 362356
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>

Conflicts:

	drivers/video/msm/vidc/1080p/ddl/vcd_ddl.c