usb: Add USB 3.1 Precision time measurement capability descriptor support

USB 3.1 devices that support precision time measurement have an
additional PTM cabaility descriptor as part of the full BOS descriptor

Look for this descriptor while parsing the BOS descriptor, and store it in
struct usb_hub_bos if it exists.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 8fc881a..6a9a0c2 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -332,6 +332,7 @@
 	struct usb_ss_cap_descriptor	*ss_cap;
 	struct usb_ssp_cap_descriptor	*ssp_cap;
 	struct usb_ss_container_id_descriptor	*ss_id;
+	struct usb_ptm_cap_descriptor	*ptm_cap;
 };
 
 int __usb_get_extra_descriptor(char *buffer, unsigned size,