LU-4976 osp: add comments for lwp_dev.c functions

LU-4976 osp: add comments for lwp_dev.c functions

Add introductory comment block for the lwp_dev.c file.
Add function comment blocks to all functions in the lwp_dev.c file.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Change-Id: I8a672982964a742d56b1d64e7b8cceb31aa64a48
Reviewed-on: http://review.whamcloud.com/10335
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Ned Bass <bass6@llnl.gov>
Reviewed-by: Richard Henwood <richard.henwood@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>