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 r257543, r264912, r264972, r264982 and r266472:
- Add preliminary support for the Realtek RTL8188EUS and RTL8188ETV chipsets.
- Add device ID for 'Sanoxy 802.11N' USB
- Initialize rssi variable.
- Fix gcc build, initialize off variable.
- The DELAY() should not be used in USB drivers.
- The usb_pause_mtx() function takes ticks and not milliseconds as last argument.

Add preliminary support for the Realtek RTL8188EUS and RTL8188ETV chipsets.

Committed over the TP-LINK TL-WN725N v2 (RTL8188EUS) on amd64 with WPA.