get rid of pointless checks for dentry->sb == NULL

it never is...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/security/tomoyo/realpath.c b/security/tomoyo/realpath.c
index d1e05b0..8d95e91 100644
--- a/security/tomoyo/realpath.c
+++ b/security/tomoyo/realpath.c
@@ -103,7 +103,7 @@
 		if (!buf)
 			break;
 		/* Get better name for socket. */
-		if (dentry->d_sb && dentry->d_sb->s_magic == SOCKFS_MAGIC) {
+		if (dentry->d_sb->s_magic == SOCKFS_MAGIC) {
 			struct inode *inode = dentry->d_inode;
 			struct socket *sock = inode ? SOCKET_I(inode) : NULL;
 			struct sock *sk = sock ? sock->sk : NULL;