USB: f_mtp: Set maximum burst value to two for superspeed mode

Currently burst value is set to zero for superspeed in mtp driver.
MTP throughput can be improved by setting max burst vlaue to non
zero value in superspeed mode. Hence set max burst vlaue to two
for both IN and OUT bulk endpoints in superspeed mode.

CRs-Fixed: 532070
Change-Id: Ib78b8fec5d1ab934f4d4ec80b7e008149707ce0f
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>
USB: gadget: rndis: Optimize tx path for better performance

Current rndis header addition and aggregation steps:
1. Increase skb headroom by size of rndis header.
2. Copy skb data with newly created skb having more headroom.
3. Create and add rndis header with it.
4. Again copy skb data with usb request buffer for aggregation purpose.

New optimized steps :
1. Create and copy rndis header directly with usb request buffer
2. Copy skb data with usb request buffer

Above new steps avoids cpu intensive skb operations which reduces CPU
usage and provide better throughput.

This change also assigns completion handle with usb request at the time
of usb request creation instead of assigning everytime before queueing
usb request.

CRs-Fixed: 551363
Change-Id: Ifc64d6a8573f6a24e28c73ef9a19b62649e171cd
Signed-off-by: Mayank Rana <mrana@codeaurora.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>