drm/amd/display: Fix DMUB errors introduced by DML2

When DML 2 was introduced, it changed part of the generic sequence of
DC, which caused issues on previous DCNs with DMUB support. This commit
ensures the new sequence only works for new DCNs from 3.5 and above.

Changes since V1:
- Harry: Use the attribute using_dml2 instead of check the DCN version.

Cc: Vitaly Prosyak <vprosyak@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Qingqing Zhuo <Qingqing.Zhuo@amd.com>
Cc: Daniel Wheeler <daniel.wheeler@amd.com>
Cc: Alex Deucher <Alexander.Deucher@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Fixes: 7966f319 ("drm/amd/display: Introduce DML2")
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>