LU-7623 Add __user to seq_write buffer arguments

LU-7623 Add __user to seq_write buffer arguments

Updates whole tree and adds forgotten __user attribute,
syncs up prototypes and such.
This keeps sparse happy and helps to ensure user/kernel pointers
correctness.

Change-Id: I54cf7479fffbd8ce211b28f9f3a9de81f600a32e
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/17788
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Frank Zago <fzago@cray.com>