Fix 5780 PHY related problems:

1. MAC_RX_MODE reset must be done before setting up the MAC_MODE
   register on 5705_PLUS chips or the chip will stop receiving after
   a while. The MAC_RX_MODE reset is needed to prevent intermittently
   losing the first receive packet on serdes chips.

2. Skip MAC loopback test on 5780 because of hardware errata. Normal
   traffic including PHY loopback is not affected by the errata.

3. PHY loopback fails intermittently on 5708S and this is fixed by
   putting the PHY in loopback mode first before programming the MAC
   mode register. A MAC_RX_MODE reset is also added.

4. Return -EINVAL in tg3_nway_reset() if device is in TBI mode. Allow
   nway_reset if 5780S is in parallel detect mode.

5. Add missing PHY IDs in KNOWN_PHY_ID() macro.
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>