eco32: use 0xfb000000 as illegal instruction instead of 0xfc000000

The __UCLIBC_ABORT_INSTRUCTION__ is used to initiate a suicide,
and inserting an illegal instruction will cause a SIGILL to be
sent.
Both 0xfc000000 and 0xfb000000 are illegal instructions,
and I'm changing this for purely egoistical reasons.
I have used 0xfc000000 as an exit simulation instruction
in my hacked version of the eco32 functional simulator.
eco32: syscalls: add arguments to outgoing reg list

This is needed to tell the compiler that those registers
are being clobbered, and it will not allow you to have incoming
registers in the clobber list.