igb: reset sgmii phy at start of init

Our SGMII phy code was incomplete in that it was not actually placing the
phy in SGMII mode and as a result the PHY was not able to establish a link
when connected to a non serdes link partner.  This patch updates the code
to combine the SGMII/serdes PCS init and to add the necessary reset.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>