The x18 register isn't useable within FreeBSD kernel space, so we
have to fix the BLAKE3 aarch64 assembly for not using it.
The source files are here: https://github.com/mcmilk/BLAKE3-tests
Reviewed-by: Kyle Evans <kevans@FreeBSD.org>
Signed-off-by: Tino Reichardt <milky-zfs@mcmilk.de>
Closes#14728