LU-12331 llite: create obd_device with usercopy whitelist

LU-12331 llite: create obd_device with usercopy whitelist

Since kernel 4.16 hardened usercopy has been added,
whitelist the struct obd_device to silence the warning.

 Bad or missing usercopy whitelist? Kernel memory exposure attempt
 detected from SLUB object 'll_obd_dev_cache' (offset 1256, size 40)!
 WARNING: CPU: 1 PID: 17534 at mm/usercopy.c:83 usercopy_warn+0x7d/0xa0
 Call Trace:
   __check_object_size+0xfa/0x181
   lmv_iocontrol+0x1146/0x1880 [lmv]
   ll_obd_statfs+0x356/0x860 [lustre]
   ll_dir_ioctl+0x1e37/0x6760 [lustre]
   do_vfs_ioctl+0xa4/0x630

Linux-commit: 8eb8284b412906181357c2b0110d879d5af95e52

Test-Parameters: trivial
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Change-Id: Ie863e8a5e2cebd3fd716e7ccc4e0491f83f6fabc
Reviewed-on: https://review.whamcloud.com/34946
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>