axnet_cs: Fix build after net device ops ne2k conversion.

Commit 4e4fd4e485ad63a9074ff09a9b53ffc7a5c594ec ("ne2k: convert to
net_device_ops") exported some ei_* symbols from the 8390 library,
but the axnet_cs driver defines local static versions of the same
functions.

Rename them to avoid the namespace conflict.

Reported by Stephen Rothwell.

Signed-off-by: David S. Miller <davem@davemloft.net>