le*dec / le*enc functions.
Replace net80211 specific macros with system-wide bytestream
encoding/decoding functions:
- LE_READ_2 -> le16dec
- LE_READ_4 -> le32dec
- LE_WRITE_2 -> le16enc
- LE_WRITE_4 -> le32enc
+ drop ieee80211_input.h include, where it was included for these
operations only.
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D6030