drm/dp_mst: Rename drm_dp_mst_atomic_check_topology_state

[why]
drm_dp_mst_atomic_check_topology_state() should be renamed
to reflect more specific type of check. Since it is verifying
payload allocation limit it should be renamed into
drm_dp_mst_atomic_check_vcpi_alloc_limit()

Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>