MIPS: Detect DSP v3 support

DSPv3 is supported on all MIPSr6 systems which indicate support for DSPv2.

This doesn't require any changes to the kernel's handling of DSP
resources. The patch is to detect support and indicate it in /proc/cpuinfo

DSP v3 introduces a new instruction BPOSGE32C

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12918/


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