cgroup_do_mount(): massage calling conventions
pass it fs_context instead of fs_type/flags/root triple, have
it return int instead of dentry and make it deal with setting
fc->root.
Signed-off-by: 
Al Viro <viro@zeniv.linux.org.uk>
pass it fs_context instead of fs_type/flags/root triple, have
it return int instead of dentry and make it deal with setting
fc->root.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>