Revert "serial: 8250: Let serial core initialise spin lock"

This reverts commit 679193b7.

It appears that in QEmu the lock has been initialised differently
(it wasn't obvious on real hardware during testing). Let's
revert the change until the better approach will be developed.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200802111612.36189-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -3194,6 +3194,7 @@ 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);