dmaengine: stm32-mdma: fix spelling mistake: "avalaible" -> "available"

Trivial fix to spelling mistake in dev_err error message text and make
channel plural.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/stm32-mdma.c

@@ -1521,7 +1521,7 @@ static struct dma_chan *stm32_mdma_of_xlate(struct of_phandle_args *dma_spec,
 
 	c = dma_get_any_slave_channel(&dmadev->ddev);
 	if (!c) {
-		dev_err(mdma2dev(dmadev), "No more channel avalaible\n");
+		dev_err(mdma2dev(dmadev), "No more channels available\n");
 		return NULL;
 	}