staging: fsl-dpaa2/eth: Remove dead code

All possible values of the switch statement are explicitly
handled, so there's no need to have a default branch.

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