mdss: dp: avoid notifying DP connect during AUX timeout cases

In case the DPCD read transaction continuously times out, it is
likely that the sink is not responding or the DP cable/dongle is
faulty and hence no response is seen. In such cases, avoid
reporting the DP connect event to userspace.

Change-Id: Ie07de464f63dc3b18c875a061a18ad00e4c99e85
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>