drm/msm/dp: remove dp_display_post_open operations

The current driver implementation delays the connect_work until drm client
initializations are complete. This is performed to avoid sending hpd event
notification to drm client when hpd is connected before drm client is
initialized as it may cause drm client to miss the hpd event notification
and may not able to create the display. This delayed connect_work not
required anymore as drm client can handle plug-in display creation based
on the connector status reported from drm_get_connector api.

This change removes dp_display_post_open operations from driver
as this functionality is not required anymore as explained.

CRs-Fixed: 2372565
Change-Id: Id6a5558c49a0b941209ab9e4b0a0a45154dfc118
Signed-off-by: Govinda Rajulu Chenna <gchenna@codeaurora.org>
Signed-off-by: Fuad Hossain <fhossain@codeaurora.org>