[MIPS] Make PROT_WRITE imply PROT_READ.

arch/mips/mm/fault.c

@@ -89,7 +89,7 @@ good_area:
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
 	} else {
-		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
+		if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
 			goto bad_area;
 	}