msm: vidc: Increase max buffers to VB2_MAX_FRAME (i.e. 64)

It's an arbitrary limit anyway.  Increase it to satisfy some clients
that'd like more buffers.

Change-Id: Ia1e0afd09089b6303b6590de804ea509b01626f4
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>