i.MX6Q: isiot: Switch the mmc env based on devno

Add board_mmc_get_env_dev

Switch the mmc env based on the mmc devno, instead of separately
defining a config item in include/configs using board_mmc_get_env_dev
- devno 0: sd/esd
- devno 1: mmc/emmc

Cc: Stefano Babic <sbabic@denx.de>
Cc: Matteo Lisi <matteo.lisi@engicam.com>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>

board/engicam/icorem6_rqs/icorem6_rqs.c

@@ -47,6 +47,12 @@ int board_init(void)
 }
 
 #ifdef CONFIG_ENV_IS_IN_MMC
+int board_mmc_get_env_dev(int devno)
+{
+	/* dev 0 for SD/eSD, dev 1 for MMC/eMMC */
+	return (devno == 3) ? 1 : 0;
+}
+
 static void mmc_late_init(void)
 {
 	char cmd[32];