MIPS: Add BMIPS CP0 register definitions

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Cc: mbizon@freebox.fr
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Tested-by: Florian Fainelli <ffainelli@freebox.fr>
Patchwork: https://patchwork.linux-mips.org/patch/1708/


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