memblock: Make a boundary tighter in memblock_add_range().

When type->cnt * 2 + 1 is less than or equal to type->max, there is
enough empty regions to insert.

Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Link: https://lore.kernel.org/r/20230129090034.12310-2-zhangpeng.00@bytedance.com


Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>