[TG3]: Fix low power state

Fix the following bugs in tg3_set_power_state():

1. Both WOL and ASF flags require switching to aux power.

2. Add a missing handshake with firmware to enable WOL.

3. Turn off the PHY if both WOL and ASF are disabled.

4. Add nvram arbitration before halting the firmware.

5. Fix tg3_setup_copper_phy() to switch to 100Mbps when
   changing to low power state.

Update revision and date.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>