fix for lcov test for mips little endian

[Justin Bogner]

reed kotler <rkotler at mips.com> writes:
> Change xfail condition so that it works properly for little endian Mips.
>
> Mips was added to the list of xfail targers but only big endian mips
> should have been added.
>
> Per the suggest of Daniel Sanders, this fixes the issues and I have
> checked it on our little endian Mips machines.

LGTM.