x86, pat: In rbt_memtype_check_insert(), update new->type only if valid

new->type should only change when there is a valid ret_type. Otherwise
the requested type and return type should be same.

Signed-off-by: Venkatesh Pallipadi <[e-mail]>
LKML-Reference: <[e-mail]>
Tested-by: Jack Steiner <[e-mail]>
Signed-off-by: H. Peter Anvin <[e-mail]>

arch/x86/mm/pat_rbtree.c

···
 						new->type, ret_type);
 
 	if (!err) {
-		new->type = *ret_type;
+		if (ret_type)
+			new->type = *ret_type;
+
 		memtype_rb_insert(&memtype_rbroot, new);
 	}
 	return err;