serial: 8250_mid: include missed linux/bitops.h

The BIT() macro, that is definded in bitops.h, is used in the driver. Include
necessary header for that.

While here, reorder included headers alphabetically.

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>