MIPS: Probe the P6600 core

Support probing the P6600 core now that cases for handling it have been
added throughout the core MIPS kernel code.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Maciej W. Rozycki <macro@imgtec.com>
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12344/


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