cifs: Fix inconsistent IS_ERR and PTR_ERR

Fix inconsistent IS_ERR and PTR_ERR in cifs_find_swn_reg(). The proper
pointer to be passed as argument to PTR_ERR() is share_name.

This bug was detected with the help of Coccinelle.

Fixes: bf80e5d ("cifs: Send witness register and unregister commands to userspace daemon")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Samuel Cabrero <scabrero@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifs_swn.c

@@ -272,7 +272,7 @@ static struct cifs_swn_reg *cifs_find_swn_reg(struct cifs_tcon *tcon)
 	if (IS_ERR(share_name)) {
 		int ret;
 
-		ret = PTR_ERR(net_name);
+		ret = PTR_ERR(share_name);
 		cifs_dbg(VFS, "%s: failed to extract share name from target '%s': %d\n",
 				__func__, tcon->treeName, ret);
 		kfree(net_name);