x86, mm: Unifying after_bootmem for 32bit and 64bit

x86, mm: Unifying after_bootmem for 32bit and 64bit

after_bootmem has different meaning in 32bit and 64bit.
        32bit: after bootmem is ready
        64bit: after bootmem is distroyed
Let's merget them make 32bit the same as 64bit.

for 32bit, it is mixing alloc_bootmem_pages, and alloc_low_page under
after_bootmem is set or not set.

alloc_bootmem is just wrapper for memblock for x86.

Now we have alloc_low_page() with memblock too. We can drop bootmem path
now, and only alloc_low_page only.

At the same time, we make alloc_low_page could handle real after_bootmem
for 32bit, because alloc_bootmem_pages could fallback to use slab too.

At last move after_bootmem set position for 32bit the same as 64bit.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-40-git-send-email-yinghai@kernel.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>