MIPS: Add arch CDMM definitions and probing

Add architectural definitions and probing for the MIPS Common Device
Memory Map (CDMM) region. When supported and enabled at a particular
physical address, this region allows some number of per-CPU devices to
be discovered and controlled via MMIO.

A bit exists in Config3 to determine whether the feature is present, and
a CDMMBase CP0 register allows the region to be enabled at a particular
physical address.

[ralf@linux-mips.org: Sort conflict with other patches.]

Signed-off-by: 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/9178/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cpu-probe.c

@@ -441,6 +441,8 @@ static inline unsigned int decode_config3(struct cpuinfo_mips *c)
 		c->htw_seq = 0;
 		c->options |= MIPS_CPU_HTW;
 	}
+	if (config3 & MIPS_CONF3_CDMM)
+		c->options |= MIPS_CPU_CDMM;
 
 	return config3 & MIPS_CONF_M;
 }