arm64/vmm: Move nVHE-only code to the new file
There are some functions that are only needed in non-VHE mode. These
are used to handle hypervisor calls from the kernel, and to manage the
page tables in EL2. As these won't be used by the VHE code we can move
them to the non-VHE specific files.
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D46073