usb: rndis: Add ul aggregation stats info to debug files

Enable UL aggregation stats to be accessed from debug
files. Also fix the minor issue with counting number of
packets during ul de-aggregation.

Change-Id: Ibfb0e2ee537e3dfbf583201bf79d5b8bcc5865a5
Signed-off-by: Vamsi Krishna <vskrishn@codeaurora.org>
Signed-off-by: Sivasri Kumar Vanka <sivasri@codeaurora.org>