x86: Sanity check the e820 against the SRAT table using e820 map only

node_cover_memory() sanity checks the SRAT table by ensuring that all
PXMs cover the memory reported in the e820.

However, when calculating the size of the holes in the e820, it uses
the early_node_map[] which contains information taken from both SRAT
and e820. If the SRAT is missing an entry, then it is not detected
that the SRAT table is incorrect and missing entries.

This patch uses the e820 map to calculate the holes instead of
early_node_map[].

comment is from Mel.

[ Impact: reject incorrect SRAT tables ]

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4A03E10C.60906@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>