msm: vidc: Limit max supported instances in driver

Currently the limit for max supported instances is in venus.
When we reach this limit, H/W reports session_error for the
new session. This is different than normal session_error
and we need to handle it differently. So, Reject the session if
the new instance exceeds in driver itself to make error handling
easy.

Also add a secure count to restrict the number of secure
instances opened concurrently due to some system wide
limitations on resources.

Change-Id: Icda379d3f3b6a8f6be5e471c378a73920a1c1b58
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>
Signed-off-by: Shalaj Jain <shalajj@codeaurora.org>