ide: add ->dma_check method

* Add (an optional) ->dma_check method for checking if DMA can be
  used for a given command and fail DMA setup in ide_dma_prepare()
  if necessary.

* Convert alim15x3 and trm290 host drivers to use ->dma_check.

* Rename ali15x3_dma_setup() to ali_dma_check() while at it.

There should be no functional changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/include/linux/ide.h b/include/linux/ide.h
index 78892e2a..b350667 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -717,6 +717,7 @@
 	int	(*dma_test_irq)(struct ide_drive_s *);
 	void	(*dma_lost_irq)(struct ide_drive_s *);
 	/* below ones are optional */
+	int	(*dma_check)(struct ide_drive_s *, struct ide_cmd *);
 	int	(*dma_timer_expiry)(struct ide_drive_s *);
 	void	(*dma_clear)(struct ide_drive_s *);
 	/*