KVM: arm64: Hook up ->page_count() for hypervisor stage-1 page-table

kvm_pgtable_hyp_unmap() relies on the ->page_count() function callback
being provided by the memory-management operations for the page-table.

Wire up this callback for the hypervisor stage-1 page-table.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211215161232.1480836-5-qperret@google.com

arch/arm64/kvm/hyp/nvhe/setup.c

@@ -257,6 +257,7 @@ void __noreturn __pkvm_init_finalise(void)
 		.virt_to_phys = hyp_virt_to_phys,
 		.get_page = hpool_get_page,
 		.put_page = hpool_put_page,
+		.page_count = hyp_page_count,
 	};
 	pkvm_pgtable.mm_ops = &pkvm_pgtable_mm_ops;