iwlwifi: rename IWL_MAX_CMD_TFDS to IWL_MAX_CMD_TBS_PER_TFD

The IWL_MAX_CMD_TFDS name for this constant is wrong, the
constant really indicates how many TBs we can use in the
driver for a single command TFD, rename the constant and
also add a comment explaining it.

Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-devtrace.h b/drivers/net/wireless/iwlwifi/iwl-devtrace.h
index 10f0179..81aa91f 100644
--- a/drivers/net/wireless/iwlwifi/iwl-devtrace.h
+++ b/drivers/net/wireless/iwlwifi/iwl-devtrace.h
@@ -363,7 +363,7 @@
 		__entry->flags = cmd->flags;
 		memcpy(__get_dynamic_array(hcmd), hdr, sizeof(*hdr));
 
-		for (i = 0; i < IWL_MAX_CMD_TFDS; i++) {
+		for (i = 0; i < IWL_MAX_CMD_TBS_PER_TFD; i++) {
 			if (!cmd->len[i])
 				continue;
 			memcpy((u8 *)__get_dynamic_array(hcmd) + offset,