KVM: arm64: Replace force_pte with a max_map_size attribute

KVM: arm64: Replace force_pte with a max_map_size attribute

force_pte is annoyingly limited in what it expresses, and we'd
be better off with a more generic primitive. Introduce max_map_size
instead, which does the trick and can be moved into the vma_info
structure. This firther allows it to reduce the scopes in which
it is mutable.

Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>