imx8: add cpu support

Add cpu type and Kconfig entry

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/imx8/cpu.c b/arch/arm/mach-imx/imx8/cpu.c
index 4bbc956..2c42535 100644
--- a/arch/arm/mach-imx/imx8/cpu.c
+++ b/arch/arm/mach-imx/imx8/cpu.c
@@ -542,6 +542,8 @@
 	case MXC_CPU_IMX8QXP:
 	case MXC_CPU_IMX8QXP_A0:
 		return "QXP";
+	case MXC_CPU_IMX8QM:
+		return "QM";
 	default:
 		return "??";
 	}
@@ -613,6 +615,7 @@
 
 static const struct udevice_id cpu_imx8_ids[] = {
 	{ .compatible = "arm,cortex-a35" },
+	{ .compatible = "arm,cortex-a53" },
 	{ }
 };