msm: vidc: Use correct extradata size for DPB allocation

Extradata size is no longer stored instance buffreq
structure. So, during DPB allocation use the size stored
in instances bufq structure which is updated correctly.

Change-Id: I65c3d8371d599ba7755a8c4012734e412d55ac89
Signed-off-by: Vaibhav Deshu Venkatesh <vdeshuve@codeaurora.org>