tg3: Fix EEE interoperability workaround

Commit 21a00ab2, entitled
"tg3: Fix EEE interoperability issue", added an EEE interoperability
fix.  We found that the fix doesn't work if applied too early though.
This patch delays the fix until right before allowing LPI assertion.

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