DM USB: fix guest kernel short packets warning

There are many 'short packet' warnings in the UOS kernel dmesg output,
which are result from bad short packet identification algorithm. This
patch is used to fix it.

Change-Id: Idfa0b87fc96893b80d5c9fe8dab4db35aa5bfe84
Tracked-On:
Signed-off-by: Xiaoguang Wu <xiaoguang.wu@intel.com>
Reviewed-by: Liang Yang <liang3.yang@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>

Author: xiaoguangwu

devicemodel/hw/platform/usb_pmapper.c

@@ -106,6 +106,13 @@ usb_dev_comp_req(struct libusb_transfer *libusb_xfer)
 	for (i = 0; i < req->blk_count; i++) {
 		done = 0;
 		block = &xfer->data[idx % USB_MAX_XFER_BLOCKS];
+
+		/* Link TRB need to be skipped */
+		if (!block->buf || !block->blen) {
+			idx = (idx + 1) % USB_MAX_XFER_BLOCKS;
+			continue;
+		}
+
 		if (len > buf_idx) {
 			done = block->blen;
 			if (done > len - buf_idx) {
@@ -203,6 +210,7 @@ usb_dev_prepare_xfer(struct usb_data_xfer *xfer, int *count, int *size)
 
 		if (block->processed) {
 			idx = (idx + 1) % USB_MAX_XFER_BLOCKS;
+			c++;
 			continue;
 		}
 		if (block->buf && block->blen > 0) {