msm: vidc: Print out buffer count in debugfs

The buffer count is useful information when debugging.  As such print it
out when `cat <debug>/msm_vidc/core*/inst_*/info` is run.

Change-Id: If1b11e17d2aa66f987c7005c80bf6230f890ef8a
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>