net80211 & wireless drivers: remove duplicate defines (noop)

• IEEE80211_DIR_DSTODS(wh) -> IEEE80211_IS_DSTODS(wh).
• N(a) -> nitems(a).
• Remove LE_READ_2(p)/LE_READ_4(p) definitions (and include ieee80211_input.h instead).
• <drvname>_TXOP_TO_US(txop) -> IEEE80211_TXOP_TO_US(txop).
• Put IEEE80211_RV(v) into ieee80211_proto.h and remove local RV(v) definitions.

Submitted by: Andriy Voskoboinyk <s3erios@gmail.com>
Differential Revision: https://reviews.freebsd.org/D3705