8250: add support for ASIX devices with a FIFO bug

Information and a different patch provided by <donald@asix.com.tw>. We do
it a little differently to keep the modularity and to avoid playing with
RLSI.

We add a new uart bug for the parity flaw and set it in the pci matches.
If parity check is enabled then we drop the FIFO trigger to 1 as per the
Asix reference code.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>