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/sparc/Kconfig b/arch/sparc/Kconfig
index 49590f8..d211fdb 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -68,6 +68,7 @@
 	default y
 	select HAVE_IDE
 	select HAVE_OPROFILE
+	select HAVE_ARCH_KGDB if !SMP
 
 # Identify this as a Sparc32 build
 config SPARC32