Unused macro: CPU_ISR_PASSES_FRAME_POINTER

[Gedare Bloom]

Hi,
The macro CPU_ISR_PASSES_FRAME_POINTER is part of a cpu port defined
in cpu.h, but this macro seems to be unused. I don't know what the
purpose of it was intended. Anyway, it appears to be wrong for some
architectures (ARM and sparc64 at least, maybe others). Should we
remove the macro, or find a use for it and make sure it is correctly
defined for each arch?

Gedare