MFC r256718, r257410 and r257411:
- Fix RF registers for RT3070.
- Initialize BBP68 to improve RX sensitivity.
- Add RT2860_BCN_OFFSET1 and RT2860_MAX_LEN_CFG register initialization to
match with the vendor driver. While here, remove unused RT2860_DEF_MAC
definition.
MFC r253757:
Fix alignment of USB WLAN radiotap headers. This makes USB WLAN adapters
work on ARM, MIPS and similar platforms, where alignment matters.