x86-32, memblock: Make add_highpages honor early reserved ranges

Originally the only early reserved range that is overlapped with high
pages is "KVA RAM", but we already do remove that from the active ranges.

However, It turns out Xen could have that kind of overlapping to support memory
ballooning.x

So we need to make add_highpage_with_active_regions() to subtract
memblock reserved just like low ram; this is the proper design anyway.

In this patch, refactering get_freel_all_memory_range() to make it can
be used by add_highpage_with_active_regions().  Also we don't need to
remove "KVA RAM" from active ranges.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <4CABB183.1040607@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>