bnxt: simplify cls_flower command switch and handle default case

Currently the default case is not handled, which with future command
introductions would introduce a warning. So handle it and make the
switch a bit simplier removing unneeded "rc" variable.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>