usb: host: ehci: use correct device pointer for dma ops

commit a8c06e40 ("usb: separate out sysdev pointer from usb_bus")
converted to use hcd->self.sysdev for DMA operations instead of
hcd->self.controller, but forgot to do it for hcd test mode. Replace
the correct one in this commit.

Fixes: a8c06e40 ("usb: separate out sysdev pointer from usb_bus")
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>