imx: add i.MX6ULZ cpu type

Add i.MX6ULZ cpu type and helper.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
diff --git a/arch/arm/mach-imx/cpu.c b/arch/arm/mach-imx/cpu.c
index 6e9a175..73ce7f8 100644
--- a/arch/arm/mach-imx/cpu.c
+++ b/arch/arm/mach-imx/cpu.c
@@ -173,6 +173,8 @@
 		return "6UL";   /* Ultra-Lite version of the mx6 */
 	case MXC_CPU_MX6ULL:
 		return "6ULL";	/* ULL version of the mx6 */
+	case MXC_CPU_MX6ULZ:
+		return "6ULZ";	/* ULZ version of the mx6 */
 	case MXC_CPU_MX51:
 		return "51";
 	case MXC_CPU_MX53: