usb: Add support for rndis uplink aggregation

RNDIS protocol supports data aggregation on uplink and can help
reduce mips by reducing number of interrupts on device. Throughput
also improved by 20-30%. Aggregation is disabled by setting
aggregation packet size to 1. To help better UL throughput, set
as ul aggregation support to 3 rndis packets by default. It can be
configured via sysfs device attribute ul_max_pkt_per_xfer.

Change-Id: I689d37824e71835ed50bf15c3e35a0eced8f116d
Signed-off-by: Vamsi Krishna Samavedam <vskrishn@codeaurora.org>
Signed-off-by: Xerox Lin <xerox_lin@htc.com>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>