filedesc: fix missed comments about fdsetugidsafety

While here just note that both fdsetugidsafety and fdcheckstd take sleepable
locks.

sys/kern/kern_descrip.c

@@ -2088,7 +2088,7 @@ fdescfree(struct thread *td)
  * otherwise be off-limits to the process.  We check for filesystems where
  * the vnode can change out from under us after execve (like [lin]procfs).
  *
- * Since setugidsafety calls this only for fd 0, 1 and 2, this check is
+ * Since fdsetugidsafety calls this only for fd 0, 1 and 2, this check is
  * sufficient.  We also don't check for setugidness since we know we are.
  */
 static bool

sys/kern/kern_exec.c

@@ -688,10 +688,8 @@ do_execve(td, args, mac_p)
 		 * Close any file descriptors 0..2 that reference procfs,
 		 * then make sure file descriptors 0..2 are in use.
 		 *
-		 * setugidsafety() may call closef() and then pfind()
-		 * which may grab the process lock.
-		 * fdcheckstd() may call falloc() which may block to
-		 * allocate memory, so temporarily drop the process lock.
+		 * Both fdsetugidsafety() and fdcheckstd() may call functions
+		 * taking sleepable locks, so temporarily drop our locks.
 		 */
 		PROC_UNLOCK(p);
 		VOP_UNLOCK(imgp->vp, 0);