spi: mxs: cleanup wait_for_completion return handling

return type of wait_for_completion_timeout is unsigned long not int, this
patch uses the return value of wait_for_completion_timeout in the condition
directly rather than adding a additional appropriately typed variable.
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mxs.c

@@ -282,9 +282,8 @@ static int mxs_spi_txrx_dma(struct mxs_spi *spi,
 	dmaengine_submit(desc);
 	dma_async_issue_pending(ssp->dmach);
 
-	ret = wait_for_completion_timeout(&spi->c,
-				msecs_to_jiffies(SSP_TIMEOUT));
-	if (!ret) {
+	if (!wait_for_completion_timeout(&spi->c,
+					 msecs_to_jiffies(SSP_TIMEOUT))) {
 		dev_err(ssp->dev, "DMA transfer timeout\n");
 		ret = -ETIMEDOUT;
 		dmaengine_terminate_all(ssp->dmach);