FROMLIST: KVM: arm64: pkvm: Stub io map functions

Now that GICv2 is disabled in nVHE protected mode there should be no
other reason for the host to use create_hyp_io_mappings() or
kvm_phys_addr_ioremap(). Add sanity checks to make sure that assumption
remains true looking forward.

Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20211208152300.2478542-6-qperret@google.com
Bug: 209580772
Change-Id: I371533976ce9ffdbf6b0eff986680d34d3153b86