dma/imx-sdma: save irq flags when use spin_lock in sdma_tx_submit

mx53_loco: fix deadlock report from sdma_tx_submit() during boot

BugLink: http://bugs.launchpad.net/bugs/878701

Adjust to use spin_lock_irqsave()/spin_unlock_irqresotre(), so to
make it safe when called from interrupt context.
Signed-off-by: Haitao Zhang <haitao.zhang@linaro.org>
Signed-off-by: Eric Miao <eric.miao@linaro.org>
Signed-off-by: Richard Zhao <richard.zhao@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/imx-sdma.c

@@ -836,17 +836,18 @@ static struct sdma_channel *to_sdma_chan(struct dma_chan *chan)
 
 static dma_cookie_t sdma_tx_submit(struct dma_async_tx_descriptor *tx)
 {
+	unsigned long flags;
 	struct sdma_channel *sdmac = to_sdma_chan(tx->chan);
 	struct sdma_engine *sdma = sdmac->sdma;
 	dma_cookie_t cookie;
 
-	spin_lock_irq(&sdmac->lock);
+	spin_lock_irqsave(&sdmac->lock, flags);
 
 	cookie = sdma_assign_cookie(sdmac);
 
 	sdma_enable_channel(sdma, sdmac->channel);
 
-	spin_unlock_irq(&sdmac->lock);
+	spin_unlock_irqrestore(&sdmac->lock, flags);
 
 	return cookie;
 }