serial: core: Use uart_console() helper in SysRq code

Use uart_console() helper in SysRq code instead of open coded variant.
This eliminates the conditional entirely for SERIAL_CORE_CONSOLE=n case.
While here, refactor the conditional to be more compact.
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200310174337.74109-3-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial_core.c

@@ -3216,15 +3216,13 @@ int uart_handle_break(struct uart_port *port)
 	if (port->handle_break)
 		port->handle_break(port);
 
-	if (port->has_sysrq) {
-		if (port->cons && port->cons->index == port->line) {
+	if (port->has_sysrq && uart_console(port)) {
 		if (!port->sysrq) {
 			port->sysrq = jiffies + SYSRQ_TIMEOUT;
 			return 1;
 		}
 		port->sysrq = 0;
 	}
-	}
 
 	if (port->flags & UPF_SAK)
 		do_SAK(state->port.tty);