RT2880 is MIPS4Kc SoC used in many SOHO routers. This commits adds GPIO pin
control configuration of RT2880.
Submitted by: Hiroki Mori <yamori83@yahoo.co.jp>
Reviewed by: mizhka, sgalabov
Differential Revision: https://reviews.freebsd.org/D12648
The driver can read and parse the OpenWRT pinctrl dts entries.
Approved by: adrian (mentor)
Sponsored by: Smartcom - Bulgaria AD
Differential Revision: https://reviews.freebsd.org/D5999