spi/omap-mcspi: Fix the spi task hangs waiting dma_rx

The spi hangs waiting the completion of omap2_mcspi_rx_callback.
Signed-off-by: Jorge A. Ventura <jorge.araujo.ventura@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Cc: stable@vger.kernel.org

drivers/spi/spi-omap2-mcspi.c

@@ -329,7 +329,8 @@ static void omap2_mcspi_set_fifo(const struct spi_device *spi,
 disable_fifo:
 	if (t->rx_buf != NULL)
 		chconf &= ~OMAP2_MCSPI_CHCONF_FFER;
-	else
+
+	if (t->tx_buf != NULL)
 		chconf &= ~OMAP2_MCSPI_CHCONF_FFET;
 
 	mcspi_write_chconf0(spi, chconf);