iwlwifi: mvm: rs: refactor building the LQ command

Simplify the code a bit more by extracting the rates table
building logic into a separate function and handle setting
a fixed rate for debug in a separate flow.
Also avoid using and saving ucode rate format in different
places. Instead use rs_rate struct and convert to ucode format
only when filling the rates table in the LQ command.
Signed-off-by: Eyal Shapira <eyal@wizery.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/rs.h

@@ -278,7 +278,6 @@ struct iwl_scale_tbl_info {
 	struct rs_rate rate;
 	enum rs_column column;
 	s32 *expected_tpt;	/* throughput metrics; expected_tpt_G, etc. */
-	u32 current_rate;  /* rate_n_flags, uCode API format */
 	struct iwl_rate_scale_data win[IWL_RATE_COUNT]; /* rate histories */
 };