arm64: Create a TLBI invalidate for the kernel
Add pmap_s1_invalidate_all_kernel to remove the need to check for the
kernel_pmap when it's passed in.
While here replace pmap calls to cpu_tlb_flushID with
pmap_s1_invalidate_all_kernel as they are identical.
Reviewed by: kib
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D52183