atl1c: update statistics code

As Ben Hutchings pointed out for the stats in alx, some
hardware-specific stats aren't matched to the right net_device_stats
field. Also fix the collision field and include errors in the total
number of RX/TX packets.

Minor whitespace fixes to match the style in alx.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>