afs: remove unused variable 'afs_zero_fid'

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: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/fsclient.c

@@ -15,8 +15,6 @@
 #include "xdr_fs.h"
 #include "protocol_yfs.h"
 
-static const struct afs_fid afs_zero_fid;
-
 static inline void afs_use_fs_server(struct afs_call *call, struct afs_cb_interest *cbi)
 {
 	call->cbi = afs_get_cb_interest(cbi);