mm/mmap.c: __vma_adjust(): suppress uninitialized var warning

The code is OK, but it fools gcc.

mm/mmap.c:802 __vma_adjust() error: uninitialized symbol 'next_next'.

Fixes: 524e00b3 ("mm: remove rb tree.")
Reported-by: kernel test robot <lkp@intel.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmap.c

@@ -618,7 +618,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 	struct vm_area_struct *expand)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	struct vm_area_struct *next_next, *next = find_vma(mm, vma->vm_end);
+	struct vm_area_struct *next_next = NULL;	/* uninit var warning */
+	struct vm_area_struct *next = find_vma(mm, vma->vm_end);
 	struct vm_area_struct *orig_vma = vma;
 	struct address_space *mapping = NULL;
 	struct rb_root_cached *root = NULL;