iwlwifi: mvm: mark scratch area in TX command

Give the scratch area a sub structure so it's marked
explicitly and it is obvious which part it is.
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/iwlwifi/mvm/fw-api-tx.h

@@ -228,10 +228,11 @@ struct iwl_tx_cmd {
 	__le16 len;
 	__le16 next_frame_len;
 	__le32 tx_flags;
-	/* DRAM_SCRATCH_API_U_VER_1 */
+	struct {
 		u8 try_cnt;
 		u8 btkill_cnt;
 		__le16 reserved;
+	} scratch; /* DRAM_SCRATCH_API_U_VER_1 */
 	__le32 rate_n_flags;
 	u8 sta_id;
 	u8 sec_ctl;