usb: dwc3: gadget: fix DMA offset calculation

Fix offset calculation in dwc3_trb_dma_offset()
Signed-off-by: NPaul Zimmerman <paulz@synopsys.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/dwc3/gadget.c

@@ -189,7 +189,7 @@ int dwc3_send_gadget_ep_cmd(struct dwc3 *dwc, unsigned ep,
 static dma_addr_t dwc3_trb_dma_offset(struct dwc3_ep *dep,
 		struct dwc3_trb_hw *trb)
 {
-	u32		offset = trb - dep->trb_pool;
+	u32		offset = (char *) trb - (char *) dep->trb_pool;
 
 	return dep->trb_pool_dma + offset;
 }