disp: msm: dp: ensure display is disabled before deinit

When hpd disconnect is received, the dp driver sends an uevent to
usermode and waits for the usermode to tear down all external displays
before turning off the dp link. If the wait for uevent completion
times out or exits prematurely due to a race condition with the
connect path, it is possible for the dp link to be turned off
prematurely, with displays still in enabled state. On a subsequent
hpd disconnect, the driver attempts to disable the display causing
this issue since the link has been already turned off.

This change adds a check for display status after uevent handling and
before turning off dp link, to make sure the displays are always
cleaned up before the link is turned off. Any future attempts to
disable from usermode will be ignored.

Change-Id: I404ad90b037fede9c9469a2fd16ca1fbdbd36b7c
Signed-off-by: Rajkumar Subbiah <rsubbia@codeaurora.org>