usb: renesas_usbhs: disable TX IRQ before starting TX DMAC transfer

commit 6490865c upstream.

This patch adds a code to surely disable TX IRQ of the pipe before
starting TX DMAC transfer. Otherwise, a lot of unnecessary TX IRQs
may happen in rare cases when DMAC is used.

Fixes: e73a9891 ("usb: renesas_usbhs: add DMAEngine support")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/renesas_usbhs/fifo.c

@@ -932,6 +932,7 @@ static int usbhsf_dma_try_pop(struct usbhs_pkt *pkt, int *is_done)
 
 	pkt->trans = len;
 
+	usbhsf_tx_irq_ctrl(pipe, 0);
 	tasklet_init(&fifo->tasklet,
 		     usbhsf_dma_prepare_tasklet,
 		     (unsigned long)pkt);