The mt753x_bpdu_port_fw enum is globally used for manipulating the process
of deciding the forwardable ports, specifically concerning the CPU port(s).
Therefore, rename it and the values in it to mt753x_to_cpu_fw.

Change FOLLOW_MFC to SYSTEM_DEFAULT to be on par with the switch documents.
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: David S. Miller <davem@davemloft.net>