Thank you for your help. I was able to get this resolved. I had to do two things to get it to boot.
1. loading the SD card was done differently.
# assuming CONFIG_ENV_IS_IN_MMC, CONFIG_ENV_OFFSET=384KB, CONFIG_ENV_SIZE=8KB
dd if=/dev/zero of=/dev/sdc bs=512 seek=768 count=16 ;# erase uboot env at 768*512 bytes and len of 16*512 bytes
# u-boot.imx must be at offset 0x400 of boot device for booting form sd and is in the current directory.
dd if=u-boot.imx of=/dev/sdc bs=512 seek=2 ;# write uboot
2. We found a hardware issue with the SD card holder. We had two different boards that were not working but had different issues with them. Got them fixed and now it boots.