Update to v3.18.21 kernel headers.

Change-Id: If068c58cfe6ac29fab76219dbe2eb5b11cf71246
diff --git a/original/uapi/linux/usbdevice_fs.h b/original/uapi/linux/usbdevice_fs.h
index abe5f4b..019ba1e 100644
--- a/original/uapi/linux/usbdevice_fs.h
+++ b/original/uapi/linux/usbdevice_fs.h
@@ -128,11 +128,12 @@
 	char port [127];	/* e.g. port 3 connects to device 27 */
 };
 
-/* Device capability flags */
+/* System and bus capability flags */
 #define USBDEVFS_CAP_ZERO_PACKET		0x01
 #define USBDEVFS_CAP_BULK_CONTINUATION		0x02
 #define USBDEVFS_CAP_NO_PACKET_SIZE_LIM		0x04
 #define USBDEVFS_CAP_BULK_SCATTER_GATHER	0x08
+#define USBDEVFS_CAP_REAP_AFTER_DISCONNECT	0x10
 
 /* USBDEVFS_DISCONNECT_CLAIM flags & struct */