- On amd64, make vmmops_* functions globally visible, as some will be called from machine-independent code in the future.
- On arm64 and riscv, move declarations to vmm.h, since they're supposed to be generic across different VMM backends (only amd64 has more than one backend).
- Make the declaration macros consistent with each other.
- On amd64, make the function typedef names consistent with the corresponding ifunc names.
No functional change intended.