net: bcmgenet: correctly suspend and resume PHY device

Make sure that we properly suspend and resume the PHY device when we
enter low power modes. We had two calls to bcmgenet_mii_reset() which
will issue a software-reset to the PHY without using the PHY library,
get rid of them since they are completely bogus and mess up with the PHY
library state. Make sure that we reset the PHY library cached values
(link, pause and duplex) to allow the link adjustment callback to be
invoked when needed.

Fixes: b6e978e5 ("net: bcmgenet: add suspend/resume callbacks")
Fixes: 1c1008c7 ("net: bcmgenet: add main driver file")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>