ANDROID: gki_config: enable PTDUMP_STAGE2_DEBUGFS

Dump the guest stage-2 pagetables to debugfs to inspect the memory
attributes. When debugfs is mounted the following files are accessible
to display guest-VM details:

View the pagetable mappings :
cat /sys/kernel/debug/kvm/*/stage2_page_tables

View the number of IPA bits used:
cat /sys/kernel/debug/kvm/*/ipa_range

View the start level of the pagetable:
cat /sys/kernel/debug/kvm/*/stage2_levels

Bug: 260238318
Bug: 278749606
Change-Id: If157d5c3e973528ff4ae1b23433c18c5b0b0dbdd
Signed-off-by: Sebastian Ene <sebastianene@google.com>