sungem: Make PCS PHY support partially work again.

As reported by Hermann Lauer, PCS PHY support in the sungem
driver simply doesn't work.

When the chip is reset due to open, or some other similar operation,
the PCS is reset too but we don't program it back into a running
state.  The result is no link when the device is brought up.

This partially rectifies the situation for the moment, by kicking
the PCS after a sungem chip reset so that it will renegotiate and
be re-enabled again.

The behavior is still a little bit dodgy as the added renegotiate
make the link take some time after bringing the interface up,
but this is a significant improvement in that things actually work
now :-)

Based almost entirely upon an initial patch by Hermann.

Signed-off-by: David S. Miller <davem@davemloft.net>