Makefile.bsd: cleanup and sync with FreeBSD

xxhash.c was not being compiled, so when FreeBSD's kernel
switched to a newer version of ZSTD a few weeks ago, out-of-tree ZFS
failed to build

Sync module/Makefile.bsd with FreeBSD's sys/modules/zfs/Makefile

And restore the alphabetical sort in a number of places

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Yao <richard.yao@klarasystems.com>
Signed-off-by: Allan Jude <allan@klarasystems.com>
Sponsored-by: Klara, Inc.
Closes #14508