selftests: net: udpgso_bench_rx/tx: Stop when wrong CLI args are provided

Leaving unrecognized arguments buried in the output, can easily hide a
CLI/script typo. Avoid this by exiting when wrong arguments are provided to
the udpgso_bench test programs.

Fixes: 3a687bef148d ("selftests: udp gso benchmark")
Signed-off-by: Andrei Gherzan <[e-mail]>
Cc: Willem de Bruijn <[e-mail]>
Reviewed-by: Willem de Bruijn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

tools/testing/selftests/net/udpgso_bench_rx.c

···
 			cfg_verify = true;
 			cfg_read_all = true;
 			break;
+		default:
+			exit(1);
 		}
 	}
 

tools/testing/selftests/net/udpgso_bench_tx.c

···
 		case 'z':
 			cfg_zerocopy = true;
 			break;
+		default:
+			exit(1);
 		}
 	}