i.MX6UL: isiot: Add modeboot env via board_late_init

Add runtime, modeboot env which is setting mmcboot, or
nandboot based on the bootdevice so-that conditional
macros b/w MMC and NAND for CONFIG_BOOTCOMMAND should
be avoided in config files.

Cc: Matteo Lisi <matteo.lisi@engicam.com>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Reviewed by: Stefano Babic <sbabic@denx.de>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/board/engicam/isiotmx6ul/isiotmx6ul.c b/board/engicam/isiotmx6ul/isiotmx6ul.c
index 9cde4fc..0e607e0 100644
--- a/board/engicam/isiotmx6ul/isiotmx6ul.c
+++ b/board/engicam/isiotmx6ul/isiotmx6ul.c
@@ -103,6 +103,27 @@
 }
 #endif /* CONFIG_NAND_MXS */
 
+int board_late_init(void)
+{
+	switch ((imx6_src_get_boot_mode() & IMX6_BMODE_MASK) >>
+			IMX6_BMODE_SHIFT) {
+	case IMX6_BMODE_SD:
+	case IMX6_BMODE_ESD:
+	case IMX6_BMODE_MMC:
+	case IMX6_BMODE_EMMC:
+		setenv("modeboot", "mmcboot");
+		break;
+	case IMX6_BMODE_NAND:
+		setenv("modeboot", "nandboot");
+		break;
+	default:
+		setenv("modeboot", "");
+		break;
+	}
+
+	return 0;
+}
+
 int board_init(void)
 {
 	/* Address of boot parameters */