MIPS: Add CPU identifiers and probing for Cavium CN73xx and CNF75xx processors.

Add new processor identifiers for Cavium CN73xx and CNF75xx
processors, and probe for them in cpu-probe.c

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12311/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>