drm/amd/display: Remove hdcp display state with mst fix

[Why]
Due to previous code changes, displays transition from active to active
and added state immediately, making it redundant to have both display
states. Previous change to fix this caused HDCP to get into a bad state
when monitor is connected to MST hub, this change fixes that issue.

[How]
Change code behavior so when a device is added successfully the state
remains as active and when addition is unsuccessful change state to
inactive. This removes need for added and active state.

Signed-off-by: Isabel Zhang <isabel.zhang@amd.com>
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>