Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Include device rt in RT305X config.

Approved by: adrian (mentor)

Revert it back. Too many changes for one commit.

Approved by: adrian (mentor)

Include device rt in RT305X config and little cleanup.

Approved by: adrian (mentor)

Import the initial CPU support for the MIPS RALink RT305x SoC.
This is a MIPS4KC CPU with various embedded peripherals, including
wireless and ethernet support.

This commit includes the platform, UART, ethernet MAC and GPIO support.
The interrupt-driven GPIO code is disabled for now pending GPIO changes
from the submitter.

Submitted by: Aleksandr Rybalko <ray@dlink.ua>