FROMLIST: KVM: arm64: pkvm: Fix hyp_pool max order

The EL2 page allocator in protected mode maintains a per-pool max order
value to optimize allocations when the memory region it covers is small.
However, the max order value is currently under-estimated whenever the
number of pages in the region is a power of two. Fix the estimation.

Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20211208152300.2478542-2-qperret@google.com
Bug: 209580772
Change-Id: Ibb149a33cad785c777032a4d129004f619d88653