disp: msm: dp: update the connected state during clean up

Update the connected state to false during display clean up. This
will allow subsequent connections to be processed correctly in
the face of disconnect failures due to unresponsive user mode
clients.

Change-Id: If30f5d722bf742060c9d4d2dec2207d7baf27fc2
Signed-off-by: RAJAT GUPTA <rajatgu@codeaurora.org>