MIPS: Octeon: Remove dead code in __cvmx_helper_npi_probe()

This code has been marked dead for more than 10 years. Seems no need to
keep it now.

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>