x86: fix e820_update_range size when overlapping

before that we relay on sanitize_e820_map to remove the overlap.

but e820_update_range(,,E820_RESERVED, E820_RAM) will not work

this patch fix that

who is going to use this?

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