dmaengine: stm32-dmamux: Fix comment typo

The double `end' is duplicated in the comment, remove one.
Signed-off-by: Jason Wang <wangborong@cdjrlc.com>
Link: https://lore.kernel.org/r/20220811120959.18752-1-wangborong@cdjrlc.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/stm32-dmamux.c

@@ -45,7 +45,7 @@ struct stm32_dmamux_data {
 						 */
 	u32 dma_reqs[]; /* Number of DMA Request per DMA masters.
 			 *  [0] holds number of DMA Masters.
-			 *  To be kept at very end end of this structure
+			 *  To be kept at very end of this structure
 			 */
 };