WORKAROUND: ignore ARM EABI version higher than 5 in GDB

[wma_semihalf.com]

Summary

To make KGDB working, it needs to understand kernel ELF image.
By default it is compiled using EABI_5, which is not supported
on the gdb-6. As a workaround, treat these images as EABI_2 because
they share a lot of things in common.
WARNING: this workaround does not guarantee ALL funtionalities
are working, but at least makes post-mortem vmcore debugging
possible.

[jhb]

Hopefully we won't need this once devel/gdb supports arm.