ARM: KVM: fix warning in mmu.c

Compiling with THP enabled leads to the following warning:

arch/arm/kvm/mmu.c: In function ‘unmap_range’:
arch/arm/kvm/mmu.c:177:39: warning: ‘pte’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   if (kvm_pmd_huge(*pmd) || page_empty(pte)) {
                                        ^
Code inspection reveals that these two cases are mutually exclusive,
so GCC is a bit overzealous here. Silence it anyway by initializing
pte to NULL and testing it later on.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>

arch/arm/kvm/mmu.c

@@ -144,6 +144,7 @@ static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
 	while (addr < end) {
 		pgd = pgdp + pgd_index(addr);
 		pud = pud_offset(pgd, addr);
+		pte = NULL;
 		if (pud_none(*pud)) {
 			addr = kvm_pud_addr_end(addr, end);
 			continue;
@@ -174,7 +175,7 @@ static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
 		/*
 		 * If the pmd entry is to be cleared, walk back up the ladder
 		 */
-		if (kvm_pmd_huge(*pmd) || page_empty(pte)) {
+		if (kvm_pmd_huge(*pmd) || (pte && page_empty(pte))) {
 			clear_pmd_entry(kvm, pmd, addr);
 			next = kvm_pmd_addr_end(addr, end);
 			if (page_empty(pmd) && !page_empty(pud)) {