drm/amd/display: temporary clamp the vratio used to 1.0

[Why]
in Is_Support function, driver report different caps between
same timing but different scaling cause OS inconsistent.

[How]
min_row_time is a local that’s only used for verifying immediate
flip support. Clamp the vratio used for its calculation to 1.0.

Signed-off-by: Lewis Huang <Lewis.Huang@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>