x86/numa: fix c/s 20120 (Fix SRAT check for discontig memory)

x86/numa: fix c/s 20120 (Fix SRAT check for discontig memory)

That change converted the (wrong) assumption of contiguous nodes'
memory to a similarly wrong one of assuming discontiguous memory (i.e.
each node having separate E820 table entries). The code ought to be
able to deal with both, though, and I hope this change makes it so.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Alex Williamson <alex.williamson@hp.com>