kc1: Add some sysboot and devicetree-related environment variables

This adds some environment variables for sysboot and devicetree.
Signed-off-by: NPaul Kocialkowski <contact@paulk.fr>

include/configs/kc1.h

@@ -232,6 +232,8 @@
 	"boot_mmc_dev=0\0" \
 	"kernel_mmc_part=7\0" \
 	"recovery_mmc_part=5\0" \
+	"fdtfile=omap4-kc1.dtb\0" \
+	"bootfile=/boot/extlinux/extlinux.conf\0" \
 	"bootargs=console=ttyO2,115200 mem=512M\0"
 
 /*