MIPS: Refactor dumping of TLB registers for r3k/r4k

The TLB registers are dumped in a couble of places:
 - sysrq_tlbdump_single() - when dumping TLB state.
 - do_mcheck() - in response to a machine check error.

The main TLB registers also differ between r3k and r4k, but r4k appears
to be assumed.

Refactor this code into a dump_tlb_regs() function, implemented for both
r3k and r4k, and used by both of the above functions.

Fixes: d1e9a4f547 ("MIPS: Add SysRq operation to dump TLBs on all CPUs")
Suggested-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10721/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/tlbdebug.h

@@ -11,6 +11,7 @@
 /*
  * TLB debugging functions:
  */
+extern void dump_tlb_regs(void);
 extern void dump_tlb_all(void);
 
 #endif /* __ASM_TLBDEBUG_H */