drm/msm/sde: add xin halt api for vbif

This patch provides a new API call to selectively enable
and disable halting of a single VBIF port. This is needed
during recovery use cases to recover from VBIF errors and
prevent spurious requests from being serviced during
recovery operations.

Change-Id: I543cd25d9e2d9bceb2a22b5952c9123bc191fbe8
Signed-off-by: Clarence Ip <cip@codeaurora.org>