drm/amd/display: trivial comment change

FP guard is valid for all recent asics, not just RV, so fix the comment.

Reviewed-by: Chaitanya Dhere <chaitanya.dhere@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>