serial: 8250: Use UART_LCR_WLEN8 instead of literal

Use UART_LCR_WLEN8 instead of literal 0x03 in size_fifo().

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220613075736.12283-1-ilpo.jarvinen@linux.intel.com


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