fs/afs/fsclient.c:18:29: warning:
 afs_zero_fid defined but not used [-Wunused-const-variable=]

It is never used since commit 025db80c ("afs: Trace
the initiation and completion of client calls")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid Howells <dhowells@redhat.com>