[IA64] Remove sn2_defconfig.

Not really a patch as much as a remove this file request.  Now that
generic_defconfig supports all the configurations SGI currently supports
and has NR_CPUS and NR_NODES at our largest configurations, we have no
reason to maintain the extra defconfig file.
Signed-off-by: Robin Holt <holt@sgi.com>
Acked-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>