Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

Silence unused parameter warnings in fspacectl(2) bootstrap stub

While here, replace spaces with tabs and add a newline at EOF.

Fixes: 5425ba8332571e57f9fe623346cb9d83293264d4
MFC after: 3 days

truncate(1): Fix cross-build CI failure due to missing fspacectl

For other platforms, fspacectl(2) is absent. This commit masks out the
calls to fspacectl(2) and replace them with a ENODEV errno.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D31619