msm: vidc: Do not fail registration if buffer is already registered

Extradata buffers queued by client are usually from one file descriptor
with different offsets. In such cases, registering extradata buffer with
same fd but different offset might fail resulting in failure of qbuf.

Change-Id: Idcaf4865a9b7f7552631575a21ce8c45b1afe765
Signed-off-by: Vinay Kalia <vkalia@codeaurora.org>