[why]
drr is still enabled after driver is unloaded causing black screen

[how]
disable drr during pipe reset.
Signed-off-by: NWenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: NJun Lei <Jun.Lei@amd.com>
Acked-by: NLeo Li <sunpeng.li@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>