drm/msm/sde: disable sspp multirect during plane disable

Update the sspp programming for multirect during disable
updates for virtual planes. This prevents an issue with
the master plane being left in multirect mode if the
virtual plane is removed without an atomic update to the
master plane.

CRs-Fixed: 2067183
Change-Id: Iadde83cfdec19a7246e38a7eb30a6031e5ba5ddb
Signed-off-by: Clarence Ip <cip@codeaurora.org>