Kernel: Fix handful of remaining "return -EFOO" mistakes

Now that all KResult and KResultOr are used consistently throughout the
kernel, it's no longer necessary to return negative error codes.
However, we were still doing that in some places, so let's fix all those
(bugs) by removing the minuses. :^)

Kernel/TTY/TTY.cpp

@@ -465,7 +465,7 @@ KResult TTY::ioctl(FileDescription&, unsigned request, Userspace<void*> arg)
     // FIXME: When should we block things?
     //        How do we make this work together with MasterPTY forwarding to us?
     if (current_process.tty() && current_process.tty() != this) {
-        return -ENOTTY;
+        return ENOTTY;
     }
 #endif
     switch (request) {