armv8/fsl-lsch3: fdt: Check the pointer returned from call to a function may be NULL

Pointer 'reg' returned from call to function 'fdt_getprop' may be
NULL, will be passed to function and may be dereferenced there by
passing argument 1 to function 'of_read_number'. So check pointer
'reg' first.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

arch/arm/cpu/armv8/fsl-lsch3/fdt.c

@@ -33,8 +33,8 @@ void ft_fixup_cpu(void *blob)
 	off = fdt_node_offset_by_prop_value(blob, -1, "device_type", "cpu", 4);
 	while (off != -FDT_ERR_NOTFOUND) {
 		reg = (fdt32_t *)fdt_getprop(blob, off, "reg", 0);
-		core_id = of_read_number(reg, addr_cells);
 		if (reg) {
+			core_id = of_read_number(reg, addr_cells);
 			if (core_id  == 0 || (is_core_online(core_id))) {
 				val = spin_tbl_addr;
 				val += id_to_core(core_id) *