Blackfin SPI Driver: tweak magic spi dma sequence to get it working on BF54x

Without this change, SPI DMA is not reliably under stress tests.
Obiviously it's a hardware issue which is not addressed by any document.
Signed-off-by: NMike Frysinger <vapier.adi@gmail.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/spi/spi_bfin5xx.c

@@ -862,8 +862,9 @@ static void pump_transfers(unsigned long data)
 		set_dma_start_addr(drv_data->dma_channel, dma_start_addr);
 		set_dma_config(drv_data->dma_channel, dma_config);
 		local_irq_save(flags);
-		enable_dma(drv_data->dma_channel);
+		SSYNC();
 		write_CTRL(drv_data, cr);
+		enable_dma(drv_data->dma_channel);
 		dma_enable_irq(drv_data->dma_channel);
 		local_irq_restore(flags);