Add missing guard defines for simd_stat

This adds the HAVE_KERNEL_NEON and HAVE_KERNEL_FPU_INTERNAL
guards to simd_stat.c defaulted to 0 to make it build again.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Shengqi Chen <harry-chen@outlook.com>
Signed-off-by: Sebastian Wuerl <s.wuerl@mailbox.org>
Closes #16558