x86: fix 64k corruption-check

Impact: fix boot crash

Need to exit early if the addr is far above 64k.

The crash got exposed by:

  78a8b35b

: x86: make e820_update_range() handle small range update

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: <stable@kernel.org>
LKML-Reference: <49BC2279.2030101@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>