x86, e820: remove end_user_pfn

end_user_pfn used to modify the meaning of the e820 maps.

Now that all e820 operations are cleaned up, unified, tightened up,
the e820 map always get updated to reality, we don't need to keep
this secondary mechanism anymore.

If you hit this commit in bisection it means something slipped through.

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