msm: vidc: send extradata size in ftb for dynamic buffer mode

In dynamic buffer mode, since  set_buffers is not called,
extradata buffer size should be set during ftb.
Without this change, firmware will assert if extra data
is enabled.

Change-Id: I2b95b550f3d44dd6a864a1f08ef922a529806cdc
Signed-off-by: Arun Menon <avmenon@codeaurora.org>