vidc_3x: Fix cts failures

- Firmware is giving wrong number of max instances.
  Update it to 16 in driver as sdm660 supports 16 instances.
- Calculate mbpf based on output port resolution.

Change-Id: I61af5d057b58ab01cc81d18a602019d743347a77
Signed-off-by: Vasantha Balla <quic_vballa@quicinc.com>