wlan - Sync dev/netif/ral from FreeBSD

* Sync dev/netif/ral from FreeBSD, fbsd git dd885b9a0a0e, May 11 2016.

* This is a direct copy (next commit ports it to DFly)

kernel/ral: Bring in support for further chips (RT2700/2800/3090 series).

Unfortunately I don't have any hardware to test and no one volunteered
when I asked on the lists. Pushing anyway because it

kernel/ral: Bring in support for further chips (RT2700/2800/3090 series).

Unfortunately I don't have any hardware to test and no one volunteered
when I asked on the lists. Pushing anyway because it shouldn't break
RT2500/2501/2600 support. We'll see if someone reports issues with
it.

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