drm/amd/display: set ignore msa parameter only if freesync is enabled

[Why&How]

ignore_msa_timing_param is used by SubVP logic to determine if SubVP
+ DRR is possible. Linux does not support freesync on multi display
config, which results in incorrect assumption of VRR support if we
set this parameter when VRR is supported, but not enabled.

Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>