usb: musb: Fix DMA desired mode for Mentor DMA engine

Commit 754fe4a9 ("usb: musb: Remove ifdefs for TX DMA for musb_host.c")
introduces a problem setting the desired channel mode for the Mentor DMA
engine.

There is a case where an address is incorrectly assigned to the DMA
channel desired mode when it should instead be assigned the actual mode
value. This results in the value of channel->desired_mode not being
correct.
Acked-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: NCristian Birsan <cristian.birsan@microchip.com>
Signed-off-by: NJoshua Henderson <joshua.henderson@microchip.com>
Signed-off-by: NFelipe Balbi <balbi@kernel.org>

drivers/usb/musb/musb_host.c

@@ -662,7 +662,7 @@ static int musb_tx_dma_set_mode_mentor(struct dma_controller *dma,
 		csr &= ~(MUSB_TXCSR_AUTOSET | MUSB_TXCSR_DMAMODE);
 		csr |= MUSB_TXCSR_DMAENAB; /* against programmer's guide */
 	}
-	channel->desired_mode = mode;
+	channel->desired_mode = *mode;
 	musb_writew(epio, MUSB_TXCSR, csr);
 
 	return 0;