[PATCH] drivers/sn/ must be entered for CONFIG_SGI_IOC3

Actually I think this is more appropriate so we don't end up with 17
cases that add drivers/sn to the build lib.
Include drivers/sn when CONFIG_IA64_SGI_SN2 or CONFIG_IA64_GENERIC
is enabled.

Acked-by: Dave Jones <davej@redhat.com>
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>