MIPS: OCTEON: Add register definitions for cn73xx, cnf75xx and cn78xx.

These new members of the OCTEON III family have some new registers,
update some of the definitions for use in follow on patches.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12497/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>