ARM: uniphier: carry on booting for Unknown boot mode

No need to stop booting U-Boot even if boot mode is unknown.
Setting the "bootmode" environment is only useful for booting
Linux Kernel.  Anyway, U-Boot has already booted by this point.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arm/mach-uniphier/board_late_init.c

@@ -85,8 +85,8 @@ int board_late_init(void)
 		setenv("bootmode", "usbboot");
 		break;
 	default:
-		printf("Unsupported Boot Mode\n");
-		return -1;
+		printf("Unknown\n");
+		break;
 	}
 
 	uniphier_set_fdt_file();