(split) Add a note that this file is compiled as part of the kernel and libc.

Requested by:	kib
MFC after:	3 days
(split) Add missing static keyword.

MFC after:	2 weeks
(split) Style changes.
(split) On the RT2870, rf registers are now 64-bit, not 32-bit after r257955.
Committed over a Buffalo WLI-UC-AG300N (RT2870).
(split) Change run_rt2870_rf_write() prototype (no functional change)
(split) Merge branch 'CURRENT' (commit '9f3c182d')

Conflicts:
	sys/dev/usb/wlan/if_run.c