ixgbe: move disabling of relaxed ordering in start_hw()

Relaxed ordering can lead to issues with some chipsets.

This patch makes sure that it is disabled by default and
not only when DCA is on.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Evan Swanson <evan.swanson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>