imx8m: add QSPI boot dev

When boot type could not be detected from rom sw info,
read sbmr1 to detect, here we only use it to detect FLEXSPI
boot, because ROM not update it in rom sw info.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/cpu.c b/arch/arm/mach-imx/cpu.c
index af0b7fb..38b87ed 100644
--- a/arch/arm/mach-imx/cpu.c
+++ b/arch/arm/mach-imx/cpu.c
@@ -467,12 +467,14 @@
 	case BOOT_TYPE_SPINOR:
 		boot_dev = SPI_NOR_BOOT;
 		break;
-#ifdef CONFIG_IMX8M
 	case BOOT_TYPE_USB:
 		boot_dev = USB_BOOT;
 		break;
-#endif
 	default:
+#ifdef CONFIG_IMX8M
+		if (((readl(SRC_BASE_ADDR + 0x58) & 0x00007FFF) >> 12) == 0x4)
+			boot_dev = QSPI_BOOT;
+#endif
 		break;
 	}