rndis: usb: set ul aggregation support to 3 rndis packets

Currently ul aggrgation is set to support 1 rndis packet i.e
no aggregation at all. To help better UL throughput, set As ul
aggregation support to 3 rndis packets by default

Change-Id: I58575dae4b1423e8249c5b3595a80eb88c6c9cd7
Signed-off-by: Vamsi Krishna <vskrishn@codeaurora.org>