serial: 8250: do not copy port.fifosize member twice

The port.fifosize member has already been copied at 8 lines above.
Maybe the compiler optimization can clean it away, but just in case.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>