drm/amd/display: Avoid pipe split when plane is too small

[Why]
The minimum plane size we can support in DML is 16x16. If we try to pass
a 16x16 plane with dynamic pipe split then validation will fail since it
tries to split it into two pipes, each 8x8.

Some userspace doesn't check that the commit fails and because the
commit fails the old state is retained, resulting in corruption.

[How]
Add a workaround to avoid pipe split if any plane is 16x16 or smaller.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>