serial: 8250_em: Add missing break statement

Add missing break statement in serial8250_em_serial_out().

Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230227114152.22265-5-biju.das.jz@bp.renesas.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>