disp: msm: dp: fix for dp link layer cts failures

The DP link layer CTS tests issue continuous DP plug/unplug.
When that happens, sometimes the DP sw state machine is going
into a bad state causing DP blankout. This is happening when
the post_enable call fails and the hpd handling logic in the DP
driver skips sending the disconnect and next subsequent connect
notifications. This change will fix the conditions to correctly
notify the userspace about the DP connection status.

Change-Id: I41310c8c465901eb5e5bd8fdec2038fe3c01e50a
Signed-off-by: Sankeerth Billakanti <sbillaka@codeaurora.org>