fsstack/ecryptfs: remove unused get_nlinks param to fsstack_copy_attr_all

This get_nlinks parameter was never used by the only mainline user,
ecryptfs; and it has never been used by unionfs or wrapfs either.

Acked-by: Dustin Kirkland <kirkland@canonical.com>
Acked-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>