drm/msm/dp: add error handling for stream enable failures

Add error handling in the control and display modules for stream
enable failures. Ensure that the link clock is turned off if
stream enable fails, and validate the active stream count in the
stream disable path. Furthermore, disable the display core only
after the display controller is powered off in order to prevent
potential unclocked register access.

Change-Id: I4be11edbb4014b7c772b78fff871fdb4f31ce456
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>