geam6ul: 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>
Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/arch/arm/cpu/armv7/mx6/Kconfig b/arch/arm/cpu/armv7/mx6/Kconfig
index 8066aaa..7350488 100644
--- a/arch/arm/cpu/armv7/mx6/Kconfig
+++ b/arch/arm/cpu/armv7/mx6/Kconfig
@@ -257,6 +257,7 @@
 
 config TARGET_MX6UL_GEAM
 	bool "Support Engicam GEAM6UL"
+	select BOARD_LATE_INIT
 	select MX6UL
 	select OF_CONTROL
 	select DM