Etherswitch support is built by default on all SoCs except RT3662/RT3883
as they have no built-in switch and their configurations with external
switches are not yet supported.
Sponsored by: Smartcom - Bulgaria AD
Only compile what each SoC needs and get rid of MEDIATEK generic config.
Approved by: adrian (mentor)
Sponsored by: Smartcom - Bulgaria AD
Differential Revision: https://reviews.freebsd.org/D5996