[ARM] pxa: stop and disable IRQ for each DMA channels at startup

Some broken bootloaders will leave the DMA channel state unclean, which
we should really initialize correctly here.
Signed-off-by: NEric Miao <eric.miao@marvell.com>

arch/arm/mach-pxa/dma.c

@@ -121,20 +121,22 @@ int __init pxa_init_dma(int num_ch)
 	if (dma_channels == NULL)
 		return -ENOMEM;
 
-	ret = request_irq(IRQ_DMA, dma_irq_handler, IRQF_DISABLED, "DMA", NULL);
-	if (ret) {
-		printk (KERN_CRIT "Wow!  Can't register IRQ for DMA\n");
-		kfree(dma_channels);
-		return ret;
-	}
-
 	/* dma channel priorities on pxa2xx processors:
 	 * ch 0 - 3,  16 - 19  <--> (0) DMA_PRIO_HIGH
 	 * ch 4 - 7,  20 - 23  <--> (1) DMA_PRIO_MEDIUM
 	 * ch 8 - 15, 24 - 31  <--> (2) DMA_PRIO_LOW
 	 */
-	for (i = 0; i < num_ch; i++)
+	for (i = 0; i < num_ch; i++) {
+		DCSR(i) = 0;
 		dma_channels[i].prio = min((i & 0xf) >> 2, DMA_PRIO_LOW);
+	}
+
+	ret = request_irq(IRQ_DMA, dma_irq_handler, IRQF_DISABLED, "DMA", NULL);
+	if (ret) {
+		printk (KERN_CRIT "Wow!  Can't register IRQ for DMA\n");
+		kfree(dma_channels);
+		return ret;
+	}
 
 	num_dma_channels = num_ch;
 	return 0;