usb: dwc3: fix up for role switch API change

After merging the usb-gadget tree, today's linux-next build (arm
multi_v7_defconfig) failed like this:

drivers/usb/dwc3/drd.c: In function 'dwc3_setup_role_switch':
drivers/usb/dwc3/drd.c:551:23: error: assignment to 'usb_role_switch_set_t' {aka 'int (*)(struct usb_role_switch *, enum usb_role)'} from incompatible pointer type 'int (*)(struct device *, enum usb_role)' [-Werror=incompatible-pointer-types]
  551 |  dwc3_role_switch.set = dwc3_usb_role_switch_set;
      |                       ^
drivers/usb/dwc3/drd.c:552:23: error: assignment to 'usb_role_switch_get_t' {aka 'enum usb_role (*)(struct usb_role_switch *)'} from incompatible pointer type 'enum usb_role (*)(struct device *)' [-Werror=incompatible-pointer-types]
  552 |  dwc3_role_switch.get = dwc3_usb_role_switch_get;
      |                       ^

Caused by commit

  8a0a1379 ("usb: dwc3: Registering a role switch in the DRD code.")

interacting with commit

  bce3052f

 ("usb: roles: Provide the switch drivers handle to the switch in the API")

from the usb tree.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20200316143752.473f1073@canb.auug.org.au
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>