msm: mdss: wait for pipe free before returning busy error

Client waits for retire fence and reuse the pipe
on another display interface. This pipe is not
stagged on MDP hardware but software structures
are not updated because retire fence is signaled
first. Due scheduling priorities between two threads,
validate call from another interface may come first
and try to reuse the same pipe. MDSS driver fails
this call because software structures are not
updated with pipe status.

Ideally, driver should wait for timeout duration
to allow other interface (or software structure) to
release the pipe. This allow clients to reuse the
same pipe on multiple displays without switching
composition method.

Change-Id: I999874f38a829162de7708cf2e5b3b425c9d5f2a
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>