iwlwifi: revert to active table when rate is not valid

When performing rate scaling, if detected that the new rate
index is invalid, clear the search_better_tbl flag
so it will not be stuck in the loop.

Since the search table is already set up in uCode,
we need to empty out the the search table;
revert back to the "active" rate and throughput info.
Also pass the "active" table setup to uCode to make
sure the rate scale is functioning correctly.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>