While not too late rename if_get_counter_compat() to if_get_counter_default().
The compat counters will go away, but the function will remain in its place,
and in all places where it is going to be called.

Discussed with:	melifaro


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271752 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f