usb: gadget: pch_udc: fix use after free

Remove pointer dereference after free.

pci_pool_free doesn't care about contents of td.
It's just a void* for it

Addresses-Coverity-ID: 1091173 ("Use after free")
Cc: stable@vger.kernel.org
Acked-by: NMichal Nazarewicz <mina86@mina86.com>
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20191106202821.GA20347@embeddedorSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/pch_udc.c

@@ -1519,7 +1519,6 @@ static void pch_udc_free_dma_chain(struct pch_udc_dev *dev,
 		td = phys_to_virt(addr);
 		addr2 = (dma_addr_t)td->next;
 		dma_pool_free(dev->data_requests, td, addr);
-		td->next = 0x00;
 		addr = addr2;
 	}
 	req->chain_len = 1;