cpu: imx: Add i.MX 8M series SoCs

Add i.MX 8M Mini, Nano and Plus SoCs support.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
diff --git a/drivers/cpu/imx8_cpu.c b/drivers/cpu/imx8_cpu.c
index b633a2c..a35147b 100644
--- a/drivers/cpu/imx8_cpu.c
+++ b/drivers/cpu/imx8_cpu.c
@@ -31,6 +31,12 @@
 static const char *get_imx_type_str(u32 imxtype)
 {
 	switch (imxtype) {
+	case MXC_CPU_IMX8MM:
+		return "8MM";
+	case MXC_CPU_IMX8MN:
+		return "8MN";
+	case MXC_CPU_IMX8MP:
+		return "8MP";
 	case MXC_CPU_IMX8QXP:
 	case MXC_CPU_IMX8QXP_A0:
 		return "8QXP";