LU-6142 llite: create file_operations registeration function.

LU-6142 llite: create file_operations registeration function.

Create new ll_register_file_operations() to set sbi->ll_ops to the
correct struct file_operations. We can make all the struct
file_operations static.

Change-Id: I0369a4f64de5233d5272bc403f222366f9559000
Test-Parameters: trivial
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/40608
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>