x86, 32-bit: change propagate_e820_map() back to find_max_pfn()

we don't need to call memory_present that early.
numa and sparse will call memory_present later and might
even fail, it will call memory_present for the full range.

also for sparse it will call alloc_bootmem ... before we set up bootmem.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>