msm: vidc: Handle FBD's with ARF flag

For VP8 some frames are used only for decoding and not for display.
FW sends FBD with DROP_FRAME flag set for this frames.These are queued
to driver by setting DROP_FRAME flag. Clients can decide how to handle
these FBD's.

Change-Id: I278637871e4fdeef8b4089b5e04596de88a543ad
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>