drm/amd/display: Request min clocks after disabling pipes on init

[Description]
- Request min clocks after disabling pipes on init
- This optimizes for power savings during init sequence
- Also handles the case where we boot up with no display connected

Tested-by: Daniel Wheeler <Daniel.Wheeler@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alvin Lee <Alvin.Lee2@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>