ARM: 7629/1: mm: Fix missing XN flag for for MT_MEMORY_SO

Commit 8fb54284 {ARM: mm: Add strongly ordered descriptor support}
added XN flag at section level but missed it at PTE level.

Fix it by adding the L_PTE_XN to MT_MEMORY_SO PTE descriptor.
Reported-by: Richard Woodruff <r-woodruff2@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/mmu.c

@@ -283,7 +283,7 @@ static struct mem_type mem_types[] = {
 	},
 	[MT_MEMORY_SO] = {
 		.prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
-				L_PTE_MT_UNCACHED,
+				L_PTE_MT_UNCACHED | L_PTE_XN,
 		.prot_l1   = PMD_TYPE_TABLE,
 		.prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_S |
 				PMD_SECT_UNCACHED | PMD_SECT_XN,