ARM: fix executability of CMA mappings

The CMA region was being marked executable:

0xdc04e000-0xdc050000           8K     RW x      MEM/CACHED/WBRA
0xdc060000-0xdc100000         640K     RW x      MEM/CACHED/WBRA
0xdc4f5000-0xdc500000          44K     RW x      MEM/CACHED/WBRA
0xdcce9000-0xe0000000       52316K     RW x      MEM/CACHED/WBRA

This is mainly due to the badly worded MT_MEMORY_DMA_READY symbol, but
there are also a few other places in dma-mapping which should be
corrected to use the right constant.  Fix all these places:

0xdc04e000-0xdc050000           8K     RW NX     MEM/CACHED/WBRA
0xdc060000-0xdc100000         640K     RW NX     MEM/CACHED/WBRA
0xdc280000-0xdc300000         512K     RW NX     MEM/CACHED/WBRA
0xdc6fc000-0xe0000000       58384K     RW NX     MEM/CACHED/WBRA

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 0903389..4f08c13 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -333,7 +333,8 @@
 		.domain    = DOMAIN_KERNEL,
 	},
 	[MT_MEMORY_DMA_READY] = {
-		.prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY,
+		.prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |
+				L_PTE_XN,
 		.prot_l1   = PMD_TYPE_TABLE,
 		.domain    = DOMAIN_KERNEL,
 	},