module: freebsd: fix aarch64 fpu handling

Just like x86, aarch64 needs to use the fpu_kern(9) API around FPU
usage, otherwise we panic promptly at boot as soon as ZFS attempts to
do checksum benchmarking.

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Signed-off-by: Kyle Evans <kevans@FreeBSD.org>
Closes #14715