net: bcmgenet: Power up the internal PHY before probing the MII

When using the internal PHY it must be powered up when the MII is probed
or the PHY will not be detected.  Since the PHY is powered up at reset
this has not been a problem.  However, when the kernel is restarted with
kexec the PHY will likely be powered down when the kernel starts so it
will not be detected and the Ethernet link will not be established.

This commit explicitly powers up the internal PHY when the GENET driver
is probed to correct this behavior.

Fixes: 1c1008c7 ("net: bcmgenet: add main driver file")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>