usb: cdns3: Fix for incorrect DMA mask.

This patch restores the correct DMA mask after switching back to device
mode.
The issue occurred because Device part of controller use 32 bits DMA and
Host side use 64 bits DMA. During loading XHCI driver the DMA mask
used by driver is overwritten by XHCI driver so it must be restored
to 32 bits.

Reported-by: Pawel Laszczak <pawell@cadence.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Fixes: 7733f6c3

 ("usb: cdns3: Add Cadence USB3 DRD Driver")
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Tested-by: Roger Quadros <rogerq@ti.com>
Link: https://lore.kernel.org/r/1570449803-15299-1-git-send-email-pawell@cadence.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>