smack: opt_dentry is never null in in smack_d_instantiate()

This patch removes some unneeded code for if opt_dentry is null because
that can never happen.

The function dereferences "opt_dentry" earlier when it checks
"if (opt_dentry->d_parent == opt_dentry) {".  That code was added in
2008.

This function called from security_d_instantiate().  I checked all the
places which call security_d_instantiate() and dentry is always non-null.
I also checked the selinux version of this hook and there is a comment
which says that dentry should be non-null if called from
d_instantiate().
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/smack/smack_lsm.c

@@ -2191,7 +2191,7 @@ static void smack_ipc_getsecid(struct kern_ipc_perm *ipp, u32 *secid)
 
 /**
  * smack_d_instantiate - Make sure the blob is correct on an inode
- * @opt_dentry: unused
+ * @opt_dentry: dentry where inode will be attached
  * @inode: the object
  *
  * Set the inode's security blob if it hasn't been done already.
@@ -2310,20 +2310,10 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 		/*
 		 * Get the dentry for xattr.
 		 */
-		if (opt_dentry == NULL) {
-			dp = d_find_alias(inode);
-			if (dp == NULL)
-				break;
-		} else {
-			dp = dget(opt_dentry);
-			if (dp == NULL)
-				break;
-		}
-
+		dp = dget(opt_dentry);
 		fetched = smk_fetch(inode, dp);
 		if (fetched != NULL)
 			final = fetched;
-
 		dput(dp);
 		break;
 	}