nommu: stub expand_stack() for nommu case

Be consistent with VM mmap, implement expand_stack().  We can't actually do
anything other than return an error in the no MMU case though.
Signed-off-by: NGreg Ungerer <gerg@uclinux.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/nommu.c

@@ -367,6 +367,11 @@ struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
 	return find_vma(mm, addr);
 }
 
+int expand_stack(struct vm_area_struct *vma, unsigned long address)
+{
+	return -ENOMEM;
+}
+
 /*
  * look up the first VMA exactly that exactly matches addr
  * - should be called with mm->mmap_sem at least held readlocked