[PATCH, MIPS] Fix build after no_new_pseudos

[Adam Nemet]

Ian Lance Taylor writes:
> I think we should fix combine to permit splitters to create new
> pseudos.  I don't think it does us any useful service to prohibit
> them.

OK so if I understand correctly you're proposing a slight change in
the combine-backend interface.  Besides using the pseudos provided
through a clobber now even new pseudo could be used.  Then combine
would have to scan the insn for those new pseudos and update reg_stat?

Adam