dmaengine: fix comment typo

Fix comment typo.
Signed-off-by: Alexander Popov <a13xp0p0v88@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

include/linux/dmaengine.h

@@ -292,7 +292,7 @@ struct dma_chan_dev {
 };
 
 /**
- * enum dma_slave_buswidth - defines bus with of the DMA slave
+ * enum dma_slave_buswidth - defines bus width of the DMA slave
  * device, source or target buses
  */
 enum dma_slave_buswidth {