usb: musb: host: correct cppi dma channel for isoch transfer

Incorrect cppi dma channel is referenced in musb_rx_dma_iso_cppi41(),
which causes kernel NULL pointer reference oops later when calling
cppi41_dma_channel_program().

Fixes: 069a3fd1 (usb: musb: Remove ifdefs for musb_host_rx in musb_host.c
part1)

Cc: <stable@vger.kernel.org> # v4.2+
Reported-by: Matwey V. Kornilov <matwey@sai.msu.ru>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_host.c

@@ -1549,7 +1549,7 @@ static int musb_rx_dma_iso_cppi41(struct dma_controller *dma,
 				  struct urb *urb,
 				  size_t len)
 {
-	struct dma_channel *channel = hw_ep->tx_channel;
+	struct dma_channel *channel = hw_ep->rx_channel;
 	void __iomem *epio = hw_ep->regs;
 	dma_addr_t *buf;
 	u32 length, res;