When running in DCB mode, switching between link flow control and priority
flow control shouldn't need to reset the hardware.  This removes that
reset.

This also extends the set_all() dcbnl callback to return a value indicating
that the HW config changed, however a reset was not required.
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>