arm: KVM: Add S2_PMD_{MASK,SIZE} constants

They were missing, and it turns out that we do need them now.
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm/include/asm/stage2_pgtable.h

@@ -73,4 +73,7 @@ static inline bool kvm_stage2_has_pud(struct kvm *kvm)
 	return false;
 }
 
+#define S2_PMD_MASK				PMD_MASK
+#define S2_PMD_SIZE				PMD_SIZE
+
 #endif	/* __ARM_S2_PGTABLE_H_ */