omap: dma: Add read-back to DMA interrupt handler to avoid spuriousinterrupts

Flush the writes to IRQSTATUS_L0 register in the DMA interrupt handler by reading the register
directly after write. This prevents the spurious DMA interrupts noted when using VDD_OPP 1
Signed-off-by: Mathias Nyman <mathias.nyman@nokia.com>
Acked-by: Santosh Shilimkar <Santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/dma.c

@@ -1983,6 +1983,8 @@ static int omap2_dma_handle_ch(int ch)
 
 	dma_write(OMAP2_DMA_CSR_CLEAR_MASK, CSR(ch));
 	dma_write(1 << ch, IRQSTATUS_L0);
+	/* read back the register to flush the write */
+	dma_read(IRQSTATUS_L0);
 
 	/* If the ch is not chained then chain_id will be -1 */
 	if (dma_chan[ch].chain_id != -1) {