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: franciscofranco <franciscofranco.1990@gmail.com>
smp: patches from mainline 3.5 to hopefully help with hotplug
efficiency

Thomas Gleixner's generic-idle patches:

smp: Add task_struct argument to __cpu_up()
Preparatory patch to make the idle thread allocation for secondary
cpus generic.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=8239c25f47d2b318156993b15f33900a86ea5e17

smp: Add generic smpboot facility
Start a new file, which will hold SMP and CPU hotplug related generic
infrastructure.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=38498a67aa2cf8c80754b8d304bfacc10bc582b5

smp: Provide generic idle thread allocation
All SMP architectures have magic to fork the idle task and to store it
for reusage when cpu hotplug is enabled. Provide a generic
infrastructure for it.
Create/reinit the idle thread for the cpu which is brought up in the
generic code and hand the thread pointer to the architecture code via
__cpu_up().
Note, that fork_idle() is called via a workqueue, because this
guarantees that the idle thread does not get a reference to a user
space VM. This can happen when the boot process did not bring up all
possible cpus and a later cpu_up() is initiated via the sysfs
interface. In that case fork_idle() would be called in the context of
the user space task and take a reference on the user space VM.
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=29d5e0476e1c4a513859e7858845ad172f560389

arm: Use generic idle thread allocation
http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=84ec6d5796e095e2f8698bd2b5d33849ed26d9e2
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
defconfig: enable smp extensions