usb: ehci: fix memory leak in ehci_init_transfer

In ehci_init_transfer function, if the 'cpage' is bigger than 4,
it doesn't free the 'p->sgl' once allocated previously thus leading
a memory leak issue. This patch avoid this.
Signed-off-by: NLi Qiang <liqiang6-s@360.cn>
Message-id: 5821c0f4.091c6b0a.e0c92.e811@mx.google.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-ehci.c

@@ -1190,6 +1190,7 @@ static int ehci_init_transfer(EHCIPacket *p)
     while (bytes > 0) {
         if (cpage > 4) {
             fprintf(stderr, "cpage out of range (%d)\n", cpage);
+            qemu_sglist_destroy(&p->sgl);
             return -1;
         }