sfc: revert changes to NIC revision numbers

The revision enum values (eg EFX_REV_HUNT_A0) form part of our API,
 and are included in ethtool. If these are inconsistent then ethtool
 will print garbage for a register dump (ethtool -d).

Fixes: 5a6681e2 ("sfc: separate out SFC4000 ("Falcon") support into new sfc-falcon driver")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>