This commit reimplemented the NuttX32 multiboot1 wrapper:
1. Fixed the issue of SMP AP booting.
2. Reduced memory copy overhead. We only need to copy .realmode section
now.
3. Move the multiboot1 header to intel64_head.S.
Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>