media: dvb: Discard video frames with 0 length

If SDMX reports video frames with 0 length,
do no notify applications on those frames as they
can't be used for decoding anyhow.

CRs-Fixed: 564644
Change-Id: I4b93052ae154f224456f440e73586495ab418136
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>