get rid of dead code in legitimize_root()

Combination of LOOKUP_IS_SCOPED and NULL nd->root.mnt is impossible
after successful path_init().  All places where ->root.mnt might
become NULL do that only if LOOKUP_IS_SCOPED is not there and
path_init() itself can return success without setting nd->root
only if ND_ROOT_PRESET had been set (in which case nd->root
had been set by caller and never changed) or if the name had
been a relative one *and* none of the bits in LOOKUP_IS_SCOPED
had been present.

Since all calls of legitimize_root() must be downstream of successful
path_init(), the check for !nd->root.mnt && (nd->flags & LOOKUP_IS_SCOPED)
is pure paranoia.

FWIW, it had been discussed (and agreed upon) with Aleksa back when
scoped lookups had been merged; looks like that had fallen through the
cracks back then.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -729,13 +729,6 @@ static bool legitimize_links(struct nameidata *nd)
 
 static bool legitimize_root(struct nameidata *nd)
 {
-	/*
-	 * For scoped-lookups (where nd->root has been zeroed), we need to
-	 * restart the whole lookup from scratch -- because set_root() is wrong
-	 * for these lookups (nd->dfd is the root, not the filesystem root).
-	 */
-	if (!nd->root.mnt && (nd->flags & LOOKUP_IS_SCOPED))
-		return false;
 	/* Nothing to do if nd->root is zero or is managed by the VFS user. */
 	if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET))
 		return true;