video: mx3fb: Update comment for dmaengine_prep_slave_sg() API

Commit 16052827 ("dmaengine/dma_slave:
introduce inline wrappers") changed the code to use the new API, but forgot
to update a comment.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Jiri Kosina <trivial@kernel.org>
Cc: linux-fbdev@vger.kernel.org
--
v2:
  - New
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/fbdev/mx3fb.c

@@ -1179,7 +1179,7 @@ static int mx3fb_pan_display(struct fb_var_screeninfo *var,
 
 	/*
 	 * We enable the End of Frame interrupt, which will free a tx-descriptor,
-	 * which we will need for the next device_prep_slave_sg(). The
+	 * which we will need for the next dmaengine_prep_slave_sg(). The
 	 * IRQ-handler will disable the IRQ again.
 	 */
 	init_completion(&mx3_fbi->flip_cmpl);