serial: 8250: Let serial core initialise spin lock

Since the serial core handles spin lock initialisation,
let the driver rely on it.

Depends-on: f743061a ("serial: core: Initialise spin lock before use in uart_configure_port()")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200731123733.22754-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_port.c

@@ -3194,7 +3194,6 @@ void serial8250_init_port(struct uart_8250_port *up)
 {
 	struct uart_port *port = &up->port;
 
-	spin_lock_init(&port->lock);
 	port->ops = &serial8250_pops;
 	port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE);