dmaengine/ste_dma40: fix missing kernel-doc

Missing documentation creates kernel-doc warnings, so add
the documenation.

Signed-off-by: Om Prakash <omprakash.pal@stericsson.com>
Reviewed-by: Rabin Vincent <rabin.vincent@stericsson.com>
Reviewed-by: Jonas Aberg <jonas.aberg@stericsson.com>
Reviewed-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/ste_dma40.c

@@ -185,6 +185,8 @@ struct d40_base;
  * @log_def: Default logical channel settings.
  * @lcla: Space for one dst src pair for logical channel transfers.
  * @lcpa: Pointer to dst and src lcpa settings.
+ * @runtime_addr: runtime configured address.
+ * @runtime_direction: runtime configured direction.
  *
  * This struct can either "be" a logical or a physical channel.
  */