drm/amd/display: VSIF v3 set Max Refresh Rate

[WHY]
FreeSync spec requires PB8 and PB12 to be set to nominal
refresh rate regardless of fixed rate or variable

[HOW]
Removed the condition that checks and overwrites max refresh rate
and set PB8/PB12 to be set to max refresh rate always

Reviewed-by: Anthony Koo <anthony.koo@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Muhammad Ansari <muhammad.ansari@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>