drm/amd/display: re structure odm to allow 4 to 1 support

Currently odm is handled using top_bottom pipe by special casing
the differing opps to differentiate from mpc combine.

Since top/bottom pipe list was made to track mpc muxing this creates
difficulties in adding a 4 pipe odm case support.

Rather than continue using mpc combine list, this change reworks odm
to use it's own linked list to keep track of odm combine pipes. This
also opens up options for using mpo with odm, if a practical use case
is ever found.

Signed-off-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>