9p: use an IS_ERR test rather than a NULL test

Author: Julien Brunel <brunel@diku.dk>

In case of error, the function p9_client_walk returns an ERR pointer, but
never returns a NULL pointer.  So a NULL test that comes after an IS_ERR
test should be deleted.

The semantic match that finds this problem is as follows:

expression x, E;
statement S1,S2;
x = p9_client_walk(...)
... when != x = E
*  if (x != NULL)
S1 else S2

Signed-off-by: Julien Brunel 
Signed-off-by: Julia Lawall 
Signed-off-by: Eric Van Hensbergen 
Signed-off-by: Andrew Morton 

 fs/9p/vfs_inode.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index c95295c..e83aa5e 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -626,8 +626,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 	return NULL;
-	if (fid)
-		p9_client_clunk(fid);
+	p9_client_clunk(fid);
 	return ERR_PTR(result);