arm64: turn on IEEE80211 debugging and IEEE80211_SUPPORT_MESH too

[bz]

Summary

Like we do for other architectures, add IEEE80211_SUPPORT_MESH support
to the kernel config on arm64.

Like we do with, e.g., USB_DEBUG, add IEEE80211_DEBUG too on main
(std.nodebug will turn this off).

Sponsored by: The FreeBSD Foundation
X-MFC: no