sparc: Add kgdb support.

Current limitations:

1) On SMP single stepping has some fundamental issues,
   shared with other sw single-step architectures such
   as mips and arm.

2) On 32-bit sparc we don't support SMP kgdb yet.  That
   requires some reworking of the IPI mechanisms and
   infrastructure on that platform.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc64/kernel/ttable.S b/arch/sparc64/kernel/ttable.S
index b0de4c0..450053a 100644
--- a/arch/sparc64/kernel/ttable.S
+++ b/arch/sparc64/kernel/ttable.S
@@ -153,7 +153,7 @@
 tl0_resv169:	BTRAP(0x169) BTRAP(0x16a) BTRAP(0x16b) BTRAP(0x16c)
 tl0_linux64:	LINUX_64BIT_SYSCALL_TRAP
 tl0_gsctx:	TRAP(sparc64_get_context) TRAP(sparc64_set_context)
-tl0_resv170:	KPROBES_TRAP(0x170) KPROBES_TRAP(0x171) BTRAP(0x172)
+tl0_resv170:	KPROBES_TRAP(0x170) KPROBES_TRAP(0x171) KGDB_TRAP(0x172)
 tl0_resv173:	BTRAP(0x173) BTRAP(0x174) BTRAP(0x175) BTRAP(0x176) BTRAP(0x177)
 tl0_resv178:	BTRAP(0x178) BTRAP(0x179) BTRAP(0x17a) BTRAP(0x17b) BTRAP(0x17c)
 tl0_resv17d:	BTRAP(0x17d) BTRAP(0x17e) BTRAP(0x17f)