Add OCTEON constants to asm/cpu.h and asm/module.h.

Add probe function for Cavium OCTEON CPUs and hook it up.
Signed-off-by: NTomaso Paoletti <tpaoletti@caviumnetworks.com>
Signed-off-by: NDavid Daney <ddaney@caviumnetworks.com>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>