spi: omap2-mcspi: Fix DMA and FIFO event trigger size mismatch

Commit b682cffa ("spi: omap2-mcspi: Set FIFO DMA trigger level to word length")
broke SPI transfers where bits_per_word != 8. This is because of
mimsatch between McSPI FIFO level event trigger size (SPI word length) and
DMA request size(word length * maxburst). This leads to data
corruption, lockup and errors like:

	spi1.0: EOW timed out

Fix this by setting DMA maxburst size to 1 so that
McSPI FIFO level event trigger size matches DMA request size.

Fixes: b682cffa ("spi: omap2-mcspi: Set FIFO DMA trigger level to word length")
Cc: stable@vger.kernel.org
Reported-by: David Lechner <david@lechnology.com>
Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-omap2-mcspi.c

@@ -623,8 +623,8 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
 	cfg.dst_addr = cs->phys + OMAP2_MCSPI_TX0;
 	cfg.src_addr_width = width;
 	cfg.dst_addr_width = width;
-	cfg.src_maxburst = es;
-	cfg.dst_maxburst = es;
+	cfg.src_maxburst = 1;
+	cfg.dst_maxburst = 1;
 
 	rx = xfer->rx_buf;
 	tx = xfer->tx_buf;