drm/amd/display: Skip create new stream if crtc state doesn't change

Need to check if crtc state is changed so that mode set is
required before trying to create new stream.

It deals with the MST hotplug use case when plug back to the
same connector where the failure to create new stream for the
inactive crtc on the old connector.

Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>