usb: gadget: udc: renesas_usb3: fix oops in renesas_usb3_remove()

This patch fixes an issue that the renesas_usb3_remove() causes
NULL pointer dereference because the usb3_to_dev() macro will use
the gadget instance and it will be deleted before.

Fixes: cf06df3f ("usb: gadget: udc: renesas_usb3: move pm_runtime_{en,dis}able()")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>