FROMLIST: KVM: arm64: Introduce KVM_PGTABLE_S2_NOFWB Stage-2 flag

In order to further configure stage-2 page-tables, pass flags to the
init function using a new enum.

The first of these flags allows to disable FWB even if the hardware
supports it as we will need to do so for the host stage-2.

Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20210317141714.383046-2-qperret@google.com
Bug: 178098380
Change-Id: I19441d59f5bd31f6ffbefbab06c7377e29ad3246