disp: msm: dp: exit stream enable on cable disconnect

Exit stream enable on cable disconnect considering that the
controller and display modules would have transitioned to aborted
state. It is possible that the disconnect might have prevented
the link clock from being enabled, so we have to skip any register
programming in the link clock domain. We remove the unprepare
call from the DRM wrapper error handling since that path can lead
to unclocked register access when the link clock is not enabled.

Change-Id: I92595c0824193df63c2746bc8cd644f59c33604a
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>