drm/msm/dp: fix usbpd and drm framework sequence

Initialize the usbpd module after the drm connector has been
initialized. Some DisplayPort sinks or dongles can issue PD
messages with very low latency. This can cause issue during
boot up if the connector is not yet initialized and PD messages
are issued by sink or dongle.
Add a notifier to let the DisplayPort driver know that connector
has been initialized. Once the connector is initialized, initialize
the DP sub-modules to avoid boot up issues for such sinks or dongles.

CRs-Fixed: 2128730
Change-Id: If3e6b63cbecdca8828f8ddd4d9b0ec78027d6622
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>