src: unify Linux and FreeBSD large pages implem

dl_iterate_phdr(3) is also available for FreeBSD. This change adds the
same trimming code for the start and end of the .text section as on
Linux, making it work on FreeBSD, and removing the need for the
additional FreeBSD-specific check.

Manually tested on
  * https://www.osboxes.org/freebsd/#freebsd-12-1-vbox
  * https://www.osboxes.org/freebsd/#freebsd-11-vbox


  * test-digitalocean-freebsd11-x64-2

Signed-off-by: Gabriel Schulhof <gabriel.schulhof@intel.com>
PR-URL: https://github.com/nodejs/node/pull/32534


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>