drm/msm/sde: avoid enabling qseed3 with multirect

When default_scaling is enabled, qseed3 configs are
calculated and set during the atomic_commit phase.
Add validation and avoid setting qseed3 with multirect.
Part of the change, remove the qseed3/multirect validation
check, done as part of atomic_check as it might
raise false alarm on seeing the qseed3 set by the previous
atomic_commit.

Change-Id: I64601cd9d940ba1a50e4271e143455e693503e4a
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>