An interesting situation. The documentation for Orange Pi and some users on the forum recommended to compile the u-boot with a -arm-linux-gnueabihf (hardware float point).
The paradox is that I have not seen even a single worked u-boot the compiled with arm-linux-gnueabihf.
U-boot which included in the SDK does not compile with the arm-linux-gnueabihf because it contains the library compiled with the software float point.
A U-boot from sunxi-linux GIthub, compiled with a -arm-linux-gnueabihf just do not work on OPi 2 and has a size of almost two times less than the original firmware from.