[IA64] restrict CONFIG_SGI_SN_XP to IA64_GENERIC or IA64_SGI_SN2

Restrict CONFIG_SGI_SN_XP to IA64_GENERIC or IA64_SGI_SN2 kernels.
Signed-off-by: Dean Nelson <dcn@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/Kconfig

@@ -191,6 +191,7 @@ config IOSAPIC
 
 config IA64_SGI_SN_XP
 	tristate "Support communication between SGI SSIs"
+	depends on IA64_GENERIC || IA64_SGI_SN2
 	select IA64_UNCACHED_ALLOCATOR
 	help
 	  An SGI machine can be divided into multiple Single System