Use the streaming functions for reading/writing the BAP fields on wi(4).  This
fixes wi(4) device access on big endian architectures.

PR:		kern/164499
Reviewed by:	adrian
Obtained from:	NetBSD
Fix alignment of USB WLAN radiotap headers. This makes USB WLAN adapters
work on ARM, MIPS and similar platforms, where alignment matters.

MFC after:	1 week
Reported by:	XiaoQI Ge <ghw@7axu.com>