Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

MFC r267066 and r267041:
Fixes for the RSU driver:
- The R92S_TCR register is an 8-bit register. Don't access it like a
16-bit register.
- Disable parsing the delete station event, due to many false events.
- Ensure that there is only one transfer queue for each endpoint, so
to hal packets transmitted don't get out of order.
- Properly align temporary buffer to 32-bit.
- Add an extra parenthesis to make expression clear.
- Range check the association ID received from hardware.

MFC r266466, r266471, r266484, r266505, r266535 and r266542:
Fix multiple issues in the RSU driver.

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

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

Import OpenBSD's rsu(4) WLAN driver.
Support chipsets are the Realtek RTL8188SU, RTL8191SU, and RTL8192SU.

Many thanks to Idwer Vollering for porting/writing the man page and for
testing.

Reviewed by: adrian, hselasky
Obtained from: OpenBSD
Tested by: kevlo, Idwer Vollering <vidwer at gmail.com>