MAINTAINERS: add me as maintainer of MEDIATEK SWITCH DRIVER

Add me as a maintainer of the MediaTek MT7530 DSA subdriver.

List maintainers in alphabetical order by first name.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>