[etherswitch] add Marvell 88e6060 switch support

Add 88e6060 basic support: only port-based VLAN is supported.
No vlan(4) support.

Submitted by: Hiroki Mori <yamori813@yahoo.co.jp>
Reviewed by: mizhka, adrian
Approved by: adrian(mentor)
Differential Revision: https://reviews.freebsd.org/D8344