net: dsa: mt7530: fix trapping frames on non-MT7621 SoC MT7530 switch

All MT7530 switch IP variants share the MT7530_MFC register, but the
current driver only writes it for the switch variant that is integrated in
the MT7621 SoC. Modify the code to include all MT7530 derivatives.

Fixes: b8f126a8

 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
Suggested-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>