Want to write a trigger after UPDATE
Since dynamic sql is not allowed in the trigger body,you can use a statement which runs through all the columns and builds the IF statements

SELECT CONCAT('IF(OLD.',COLUMN_NAME, '=NEW.',COLUMN_NAME,' THEN
 INSERT INTO elm_activity_log (user_id, action_on, action, action_col, action_old_value, action_new_value, action_at, action_on_id) VALUES (NEW.updated_by, "company", "update", "company_name", OLD.' ,COLUMN_NAME,', NEW.',COLUMN_NAME,', CURRENT_TIMESTAMP(), NEW.company_id; END IF;')
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME='yourTable' AND column_key!='PRI';


You can narrow the results even more, take a look at COLUMNS table if you want to filter based on column type or remove columns with keys and so on.I removed the primary key columns in the last condition for example.