drm/msm/dp: fix boot-up cable notification delays

During boot-up, based on experiments, add proper delays
before sending events to user-space. User-space modules
listening for events may not be ready when the events are
sent at boot-up. Avoid missing these events by adding
necessary delays.

CRs-Fixed: 2170496
Change-Id: Iae3aa008b03df058c0c9f57f2febe042984bf921
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>