x86: Fix size for ex trampoline with 32bit

fix for error that is introduced by
| x86: Use find_e820() instead of hard coded trampoline address

it should end with PAGE_SIZE + PAGE_SIZE

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <1261525263-13763-2-git-send-email-yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>