drm/msm/dp: fix host init and deinit sequence

Initialize the host only on cable connection and de-initialize
only on cable disconnect. Keep the host initialized in the
intermediate states. DisplayPort may be powered on/off based
on interrupts received from sink. In such cases, host should
remain initialized to avoid hardware malfunctioning.

CRs-Fixed: 2087411
Change-Id: I4398eb66f6272b87e3a3d82bd5dc95c315f5c2d5
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>