arm64: KVM: PTE/PMD S2 XN bit definition

As we're about to make S2 page-tables eXecute Never by default,
add the required bits for both PMDs and PTEs.
Reviewed-by: NChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <christoffer.dall@linaro.org>

arch/arm64/include/asm/pgtable-hwdef.h

@@ -177,9 +177,11 @@
  */
 #define PTE_S2_RDONLY		(_AT(pteval_t, 1) << 6)   /* HAP[2:1] */
 #define PTE_S2_RDWR		(_AT(pteval_t, 3) << 6)   /* HAP[2:1] */
+#define PTE_S2_XN		(_AT(pteval_t, 2) << 53)  /* XN[1:0] */
 
 #define PMD_S2_RDONLY		(_AT(pmdval_t, 1) << 6)   /* HAP[2:1] */
 #define PMD_S2_RDWR		(_AT(pmdval_t, 3) << 6)   /* HAP[2:1] */
+#define PMD_S2_XN		(_AT(pmdval_t, 2) << 53)  /* XN[1:0] */
 
 /*
  * Memory Attribute override for Stage-2 (MemAttr[3:0])