atl1e: enable support for NETIF_F_RXALL and NETIF_F_RXCRC features

This patch allows (optionally, via ethtool) the atl1e NIC to:
- Receive bad frames (runt, bad-fcs, etc..)
- Receive full frames without stripping the FCS.

This has been tested on my board by injecting runt and bad-fcs
frames with a FPGA-based device.

The particular scenario of receiving very short frames (<4 bytes)
without passing FCS to the upper layer has been also tested:
This could be potentially dangerous because the driver performs a
4 byte subtraction on the frame length, but I finally have NOT
added anything to avoid this because it seems the NIC always
discards frames so much short..
If someone still have some reason to worry about this, please
tell me.. I will add an explicit SW check..

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>