LU-9121 lnet: Add the kernel level De-Marshalling API

LU-9121 lnet: Add the kernel level De-Marshalling API

Given a bulk allocated from userspace containing a
single UDSP, De-Marshalling API demarshals it
and populate the provided udsp structure.

Change-Id: I0a5a9148f8b2abc64284cb7780c37cbc8063b828
Test-Parameters: trivial testlist=lnet-selftest,sanity-lnet
Signed-off-by: Sonia Sharma <sharmaso@whamcloud.com>
Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34488
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>