ixgbevf: Fix link speed display

The ixgbevf driver would always report 10Gig speeds even when the link
speed is downshifted to 1Gig.  This patch fixes that problem.

Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>