drm/amd/display: Fix HWSS v3 fast path determination

drm/amd/display: Fix HWSS v3 fast path determination

[WHY]
We're checking surface and stream updates after they've been applied to
their respective states within `update_planes_and_stream_state`.

Medium updates under the HWSS V3 fast path that are not supported or
tested are getting implicitly if they don't trigger a DML validation
and getting updated in place on the dc->current_state context.

[HOW]
Fix this issue by moving up the fast path determination check prior
to `update_planes_and_stream_state`. This is how the V2 path works
and how the V3 path used to work prior to the refactors in this area.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>