MIPS: Probe for presence of KScratch registers.

Probe c0_config4 for KScratch registers and report them in /proc/cpuinfo.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1877/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/cpu-info.h

@@ -78,6 +78,7 @@ struct cpuinfo_mips {
 	unsigned int		watch_reg_use_cnt; /* Usable by ptrace */
 #define NUM_WATCH_REGS 4
 	u16			watch_reg_masks[NUM_WATCH_REGS];
+	unsigned int		kscratch_mask; /* Usable KScratch mask. */
 } __attribute__((aligned(SMP_CACHE_BYTES)));
 
 extern struct cpuinfo_mips cpu_data[];