tg3: Move power state transitions to init_one

The tg3 driver is going to require memory mapped register access much
sooner than before.  This patch makes sure the device is in the D0 power
state as soon as possible, and moves the code that enables the memory
arbiter outside tg3_get_eeprom_hw_cfg() where it can be more easily
monitored.

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