[S390] smsgiucv: declare char pointers as "const"

Declare the smsgiucv prefix char pointer as "const" and use
use const char pointers in callback functions.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/net/smsgiucv.h b/drivers/s390/net/smsgiucv.h
index 67f5d4f..9410b45 100644
--- a/drivers/s390/net/smsgiucv.h
+++ b/drivers/s390/net/smsgiucv.h
@@ -5,6 +5,8 @@
  * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
  */
 
-int  smsg_register_callback(char *, void (*)(char *, char *));
-void smsg_unregister_callback(char *, void (*)(char *, char *));
+int  smsg_register_callback(const char *,
+			    void (*)(const char *, char *));
+void smsg_unregister_callback(const char *,
+			      void (*)(const char *, char *));