n_hdlc: cleanup messages during registration

1) n_hdlc prints two lines during registration. Squeeze it into one.
2) prefix the error message with "N_HDLC: ", so that it's clear which
   ldisc failed to register.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200219084118.26491-5-jslaby@suse.czSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_hdlc.c

@@ -899,13 +899,13 @@ static int __init n_hdlc_init(void)
 	else if (maxframe > 65535)
 		maxframe = 65535;
 
-	pr_info("HDLC line discipline maxframe=%d\n", maxframe);
-
 	status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
 	if (!status)
-		pr_info("N_HDLC line discipline registered.\n");
+		pr_info("N_HDLC line discipline registered with maxframe=%d\n",
+				maxframe);
 	else
-		pr_err("error registering line discipline: %d\n", status);
+		pr_err("N_HDLC: error registering line discipline: %d\n",
+				status);
 
 	return status;