r8169: Support RX-ALL flag.

This allows the NIC to receive packets with bad FCS and
Runts, which can help when sniffing.

NOTE:  r8169, at least on my NIC, silently drops packets
with bad FCS instead of counting them.  It seems they are
only received in any fashion if the RxCRC flag is set
(which this patch allows).

Signed-off-by: Ben Greear <greearb@candelatech.com>