[SERIAL] Magic SysRq SAK does nothing on serial consoles

Make sysrq-K work on serial console by passing in the tty.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

include/linux/serial_core.h

@@ -415,7 +415,7 @@ uart_handle_sysrq_char(struct uart_port *port, unsigned int ch,
 #ifdef SUPPORT_SYSRQ
 	if (port->sysrq) {
 		if (ch && time_before(jiffies, port->sysrq)) {
-			handle_sysrq(ch, regs, NULL);
+			handle_sysrq(ch, regs, port->info->tty);
 			port->sysrq = 0;
 			return 1;
 		}