mm/mempolicy: remove unneeded out label

We can use unlock label to unlock ptl and return ret directly to remove
the unneeded out label and reduce the size of mempolicy.o. No functional
change intended.

[Before]
text data bss dec hex filename
26702 3972 6168 36842 8fea mm/mempolicy.o

[After]
text data bss dec hex filename
26662 3972 6168 36802 8fc2 mm/mempolicy.o

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Miaohe Lin <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

mm/mempolicy.c

···
 	}
 	page = pmd_page(*pmd);
 	if (is_huge_zero_page(page)) {
-		spin_unlock(ptl);
 		walk->action = ACTION_CONTINUE;
-		goto out;
+		goto unlock;
 	}
 	if (!queue_pages_required(page, qp))
 		goto unlock;
···
 		ret = -EIO;
 unlock:
 	spin_unlock(ptl);
-out:
 	return ret;
 }