KVM: arm64: Simplify nested VMA shift calculation

KVM: arm64: Simplify nested VMA shift calculation

In the kvm_s2_resolve_vma_size() helper, the local variable vma_pagesize
is calculated from vma_shift, only to be used to bound the vma_pagesize
by max_map_size and subsequently convert it back to a shift via __ffs().

Because vma_pagesize and max_map_size are both powers of two, we can
simplify the logic by omitting vma_pagesize entirely and bounding the
vma_shift directly using the shift of max_map_size. This achieves the
same result while keeping the size-to-shift conversion out of the helper
logic.

Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>