mdss: mdp: use file descriptor node info to track clients

FB clients are tracked using process id. The process id does
not match if open and close API callers are different. Track
the fb clients using file descriptor node id in such cases
and release all resources associated with that process id
gracefully.

CRs-fixed: 652449
Change-Id: I09c965a421197c6464a64684e9706f30df327882
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>