msm_vidc: venc: set correct count for input buffers.

Input buffer count was not set properly for video encoder driver
resulting in failure to start encoder session. This changes configures
the encoder to pick maximum of the configured buffer count and updated
buffer count.

Change-Id: Ifc25eb930be758bf690d697638255a312b2f39c6
Signed-off-by: Ashray Kulkarni <ashrayk@codeaurora.org>