serial: remove quot_frac from serial8250_do_set_divisor()

serial: remove quot_frac from serial8250_do_set_divisor()

quot_frac is unused in serial8250_do_set_divisor() since commit
b2b4b8ed3c06 (serial: 8250_exar: Move custom divisor support out from
8250_port). So no point to pass it.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20240805102046.307511-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>