staging: fsl-dpaa2/eth: Refactor interrupt arming in NAPI poll

Take into consideration the return value of napi_complete_done(),
since there might be an indication that it's not suitable to
enable driver interrupts yet.

Signed-off-by: Bogdan Purcareata <bogdan.purcareata@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>