ixgbe: do not call check_link for ethtool in ixgbe_get_settings()

In ixgbe_get_settings() the link status and speed of the interface
are determined based on a read from the LINKS register via the call
to mac.ops.check.link(). This can cause issues where external drivers
may end up with unknown speed when calling ethtool_get_setings().

Instead of calling the mac.ops.check_link() we can report the speed
from the adapter structure which is populated by the driver.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>