[IA64] update sn2_defconfig

The current sn2_defconfig is obsolete, in particular the recent ATA
changes are a pain, so here's a patch to get things in sync ... at
least for a day or two :)

Update sn_defconfig to match current community kernel tree.
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>