MIPS: Add MIPS P5600 PRid and cputype identifiers

Add a Processor ID and CPU type for the MIPS P5600 core.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6407/


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