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

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: e73a989 ("usb: renesas_usbhs: add DMAEngine support")
Cc: <stable@vger.kernel.org> # v3.1+
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/renesas_usbhs/fifo.c

@@ -890,6 +890,7 @@ static int usbhsf_dma_prepare_push(struct usbhs_pkt *pkt, int *is_done)
 
 	pkt->trans = len;
 
+	usbhsf_tx_irq_ctrl(pipe, 0);
 	INIT_WORK(&pkt->work, xfer_work);
 	schedule_work(&pkt->work);