iwlegacy: 4965-rs: cleanup il4965_rs_sta_dbgfs_rate_scale_data_read

1) remove ret local var and return the result directly
2) remove il since it is not used

Signed-off-by: Greg Dietsche <Gregory.Dietsche@cuw.edu>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>