ixgbevf: fix error code path when setting MAC address

Return error when a MAC address change is rejected by the PF.

This will prevent the user from modifying the MAC address when
that operation is not permitted.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>