isdn: isdn_tty: fix build warning of strncpy

Not upstream as isdn is long deleted.

Fix up a strncpy build warning for isdn_tty_suspend() using strscpy.

It's not like anyone uses this code anyway, and this gets rid of a build
warnings so that we can see real warnings as they pop up over time.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/isdn/i4l/isdn_tty.c

@@ -786,7 +786,7 @@ isdn_tty_suspend(char *id, modem_info *info, atemu *m)
 		cmd.parm.cmsg.para[3] = 4; /* 16 bit 0x0004 Suspend */
 		cmd.parm.cmsg.para[4] = 0;
 		cmd.parm.cmsg.para[5] = l;
-		strncpy(&cmd.parm.cmsg.para[6], id, l);
+		strscpy(&cmd.parm.cmsg.para[6], id, l);
 		cmd.command = CAPI_PUT_MESSAGE;
 		cmd.driver = info->isdn_driver;
 		cmd.arg = info->isdn_channel;