Can't Modify U-Boot Environment Variables on Updated Firmware
Yes, /tmp/deploy/images/h3ulcb is correct path. Please refer to the No13 of http://elinux.org/R-Car/Boards/Yocto-Gen3#Building_the_BSP_for_Renesas_H3ULCB.2C_M3ULCB.
All updating methods are described below. http://elinux.org/R-Car/Boards/H3SK#Flashing_firmware Could you try again?
If "u-boot" still doesn't start up please attach the log when flashing the firmware.