net80211: fix IEEE80211_DEBUG_REFCNT builds

Remove the KPI/KBI changes from ieee80211_node.h and always use the
macros to pass in func and LINE to the functions.
The actual implementations are prefixed by "_" rather than suffixed
by "_debug" as they no longer are "debug"-specific.

Some of the select functions were not actually using the passed in
func, line options; however they are calling other functions which
use them. Directly call the internal implementation in those cases
passing the arguments on.

Use a file-local debrefcnt_used define to mark the arguments unused
in cases when we compile without IEEE80211_DEBUG_REFCNT and hope the
toolchain is intelligent enough to not pass them at all in those cases.

Also _ieee80211_free_node() now has a conflict so make the previous
_ieee80211_free_node() the new __ieee80211_free_node().

Add IEEE80211_DEBUG_REFCNT to the NOTES file on amd64 to keep exercising
the option.

Sponsored by: The FreeBSD Foundation
X-MFC: never
Discussed on: freebsd-wireless
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D37529