... so can we use mem below max_low_pfn earlier.

this allows us to move several functions more early instead of waiting
to after paging_init.

That includes moving relocate_initrd() earlier in the bootup, and kva
related early setup done in initmem_init. (in followup patches)
Signed-off-by: NYinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>