The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.
Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix
They are synonymous to `kmap_atomic_prot()` and `kunmap_atomic()`
respectively.
While here, fix several style(9) issues.
Reviewed by: manu
Approved by: manu
Differential Revision: https://reviews.freebsd.org/D38155