NFSD: Remove duplicate initialization of file_lock

locks_alloc_lock() has initialized struct file_lock, no need to
re-initialize it here.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Reviewed-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>