I proposed a patch a while ago that addressed this issue. There is a bug and undocumented feature in the Hardhat objdump program. It can not convert between .bin and .srec. However there is a ppcboot option to their utility that works.
Ive been trying to compile u-boot0.4 for the mpc8266ads board. I am using the hardhat ppc-cross compiler and am coming across problems with the compilation. First of all make fails at a bootp error which can be fixed by placing parenthesis around the #define. It next fails in the examples folder where I think it is trying the hello_world.bin & others and this can be fixed by doing a chmod on each of the examples it fails on. Just wondering if anyone is coming across the same problems and if any official fixes are available for this? After I change these the project compiles ok. Cheers