ixgbe: fix slow load times on 82598 nics

Load times for NICs that use i2c to communicate with the phy were taking
~4.5 sec per port.  This fix first checks to see if the link is already
up before calling get_link_capabilities, since if it is we don't need
query the phy for link state.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>