FROMLIST: KVM: arm64: Register ptdump with debugfs on guest creation

While arch/*/mem/ptdump handles the kernel pagetable dumping code,
introduce KVM/ptdump which shows the guest stage-2 pagetables. The
separation is necessary because most of the definitions from the
stage-2 pagetable reside in the KVM path and we will be invoking
functionality **specific** to KVM.

When a guest is created, register a new file entry under the guest
debugfs dir which allows userspace to show the contents of the guest
stage-2 pagetables when accessed.

(Diff from the original patch to add a check for
is_protected_kvm_enabled)

Bug: 260238318
Bug: 278749606
Link: https://lore.kernel.org/all/20240220151035.327199-5-sebastianene@google.com/


Change-Id: Id903d8f8907390cdf53debbf5161b7a368b187ef
Signed-off-by: Sebastian Ene <sebastianene@google.com>