In easycsv_print_columns/rows, update docs

Signed-off-by: Pradana AUMARS <paumars@courrier.dev>

include/easycsv.h

@@ -167,7 +167,7 @@ easycsv_read_value(const easycsv*,
 /** 
  * Return number of rows 
  * @param[in] constant pointer to easycsv structure 
- * @return number of rows
+ * @return number of rows, -1 if error
  */
 int
 easycsv_print_rows(const easycsv*);
@@ -175,7 +175,7 @@ easycsv_print_rows(const easycsv*);
 /** 
  * Return number of columns
  * @param[in] constant pointer to easycsv structure 
- * @return number of columns
+ * @return number of columns, -1 if error
  */
 int
 easycsv_print_columns(const easycsv*);