With the BSP 2.8b2 we switched from the legacy U-Boot specific uImage format to the generic compressed Kernel image type (zImage).
The U-Boot environment must be changed to take that into account, but, to not override settings you might have in the environment we do not reset it automatically.
If you do not want to keep the environment set it to the new defaults as follows:
env default -a
saveenv
If you want to keep your environment, first print the two affected variables for your records, then set them to their new values:
printenv boot_file emmcboot
env default boot_file emmcboot
saveenv