drm/msm/sde: delay rsc pre-stop for video/wb encoders

For command mode encoders on the primary display, RSC state
transitions need to be completed before the physical encoder
is disabled. Otherwise, the RSC hardware may not be able to
complete its state transitions properly.

However, for other physical encoder types, the RSC state
updates during encoder disable may potentially enable the
RSC solver, and should be postponed until after the physical
encoders have been fully disabled.

Change-Id: I39d044ca96256dbdb478a243c709bf432abf8c62
Signed-off-by: Clarence Ip <cip@codeaurora.org>