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/include/asm/cpu-features.h

@@ -366,4 +366,8 @@
 # define cpu_has_fre		(cpu_data[0].options & MIPS_CPU_FRE)
 #endif
 
+#ifndef cpu_has_cdmm
+# define cpu_has_cdmm		(cpu_data[0].options & MIPS_CPU_CDMM)
+#endif
+
 #endif /* __ASM_CPU_FEATURES_H */