[IA64] mbcs_init() should give up unless running on sn2

CONFIG_SGI_MBCS is enabled in generic kernels, but the driver may
oops some other platforms.  Check whether we are running on sn2
and bail out if we are not before doing anything dangerous.

Acked-by: Bruce Losure <blosure@americas.sgi.com>
Signed-off-by: Greg Edwards <edwardsg@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/drivers/char/mbcs.c b/drivers/char/mbcs.c
index 3fa64c6..c268ee0 100644
--- a/drivers/char/mbcs.c
+++ b/drivers/char/mbcs.c
@@ -830,6 +830,9 @@
 {
 	int rv;
 
+	if (!ia64_platform_is("sn2"))
+		return -ENODEV;
+
 	// Put driver into chrdevs[].  Get major number.
 	rv = register_chrdev(mbcs_major, DEVICE_NAME, &mbcs_ops);
 	if (rv < 0) {