x86: Change range end to start+size

So make interface more consistent with early_res.
Later we can share some code with early_res.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <1265793639-15071-10-git-send-email-yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>