LU-14651 llite: extend inode methods with user namespace arg

Kernel 5.12 supports idmapped mounts, which extends
vfsmount struct with a new struct user_namespace member,
and also extends some inode methods with an additional
user namespace argument.

The series can be found here:
https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=idmapped_mounts

Change-Id: I7cccde8cb3288e1ce3d9b6255796b954a6e115df
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/45938
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>