tx4939ide: remove wmb()

* define CHECK_DMA_MASK
* remove use of wmb()

Reported-by: Grant Grundler <grundler@google.com>
Reviewed-by: Grant Grundler <grundler@google.com>
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>

drivers/ide/tx4939ide.c

@@ -327,15 +327,15 @@ static int tx4939ide_dma_end(ide_drive_t *drive)
 	/* read and clear the INTR & ERROR bits */
 	dma_stat = tx4939ide_clear_dma_status(base);
 
-	wmb();
+#define CHECK_DMA_MASK (ATA_DMA_ACTIVE | ATA_DMA_ERR | ATA_DMA_INTR)
 
 	/* verify good DMA status */
-	if ((dma_stat & (ATA_DMA_INTR | ATA_DMA_ERR | ATA_DMA_ACTIVE)) == 0 &&
+	if ((dma_stat & CHECK_DMA_MASK) == 0 &&
 	    (ctl & (TX4939IDE_INT_XFEREND | TX4939IDE_INT_HOST)) ==
 	    (TX4939IDE_INT_XFEREND | TX4939IDE_INT_HOST))
 		/* INT_IDE lost... bug? */
 		return 0;
-	return ((dma_stat & (ATA_DMA_INTR | ATA_DMA_ERR | ATA_DMA_ACTIVE)) !=
+	return ((dma_stat & CHECK_DMA_MASK) !=
 		ATA_DMA_INTR) ? 0x10 | dma_stat : 0;
 }