call ieee80211_crc_init() only once, when the first 802.11 device attaches instead of at every attach.
call ieee80211_crc_init() only once, when the first 802.11 device
attaches instead of at every attach.

discussed with deraadt@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars