sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

Fix building on i386 and arm. But 'public domain' headers on the files
with no creative content. Include "lost" changes from git:
o Use /dev/efi instead of /dev/efidev
o Remove redundant NULL checks.

Submitted by: kib@, dim@, zbb@, emaste@

Add a way for the architecture to specify the calling ABI for methods
in the EFI Runtime Services Table. On amd64, the calling conventions
are MS.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week