btrfs: remove duplicated leaf dirty status clearing in __push_leaf_right()

btrfs: remove duplicated leaf dirty status clearing in __push_leaf_right()

We have already called btrfs_clear_buffer_dirty() against the left leaf in
the code above:

  btrfs_set_header_nritems(left, left_nritems);

  if (left_nritems)
       btrfs_mark_buffer_dirty(trans, left);
  else
       btrfs_clear_buffer_dirty(trans, left);

So remove the second check for a 0 number of items in the left leaf and
calling again btrfs_clear_buffer_dirty() against the left leaf.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>