drm/amd/display: Run full global validation in dc_commit_state

[Why]
Dynamic link encoder assignment expects that it can modify DC
current_state and the links associated with the incoming state when
performing full validation.

This does not align with our actual synchronization constraints
in DM's atomic_check.

[How]
Since link encoder assignment only happens as part of full validation
we can just use fast validation as part of atomic_check instead.

This satisfy's DC interface requirements and skips the DML calculations
needed for pipe programming - hopefully speeding up things a little bit
to offset the cost of double validation during stream modification.

We already do this as part of dc_commit_updates_for_stream()
with validate_bandwidth(), so extend this to dc_commit_state() as
well.

Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>