[SUNSAB]: Fixup sunsab_receive_chars for when serial console isn't open (no tty)

drivers/serial/sunsab.c

@@ -101,13 +101,16 @@ static void receive_chars(struct uart_sunsab_port *up,
 			  union sab82532_irq_status *stat,
 			  struct pt_regs *regs)
 {
-	struct tty_struct *tty = up->port.info->tty;
+	struct tty_struct *tty = NULL;
 	unsigned char buf[32];
 	int saw_console_brk = 0;
 	int free_fifo = 0;
 	int count = 0;
 	int i;
 
+	if (up->port.info != NULL)		/* Unopened serial console */
+		tty = up->port.info->tty;
+
 	/* Read number of BYTES (Character + Status) available. */
 	if (stat->sreg.isr0 & SAB82532_ISR0_RPF) {
 		count = SAB82532_RECV_FIFO_SIZE;
@@ -142,6 +145,11 @@ static void receive_chars(struct uart_sunsab_port *up,
 	for (i = 0; i < count; i++) {
 		unsigned char ch = buf[i];
 
+		if (tty == NULL) {
+			uart_handle_sysrq_char(&up->port, ch, regs);
+			continue;
+		}
+
 		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
 			tty->flip.work.func((void *)tty);
 			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
@@ -217,6 +225,7 @@ static void receive_chars(struct uart_sunsab_port *up,
 		}
 	}
 
+	if (tty)
 		tty_flip_buffer_push(tty);
 
 	if (saw_console_brk)