net80211: fix IEEE80211_FHT_BITS

AMPDU_RX was added as a second AMPDU_TX, LDPC_TX and LDPC_RX missing;
correct and add missing.
Makes ddb output (and other debugging) look more correct.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D45505