x86: fix NUMA handling (c/s 20599:e5a757ce7845)

x86: fix NUMA handling (c/s 20599:e5a757ce7845)

c/s 20599 caused the hash shift to become significantly smaller on
systems with an SRAT like this

(XEN) SRAT: Node 0 PXM 0 0-a0000
(XEN) SRAT: Node 0 PXM 0 100000-80000000
(XEN) SRAT: Node 1 PXM 1 80000000-d0000000
(XEN) SRAT: Node 1 PXM 1 100000000-130000000

Comined with the static size of the memnodemap[] array, NUMA got
therefore disabled on such systems. The backport from Linux was really
incomplete, as Linux much earlier had already introduced a dynamcially
allocated memnodemap[].

Further, doing to/from pdx translations on addresses just past a valid
range is not correct, as it may strip/fail to insert non-zero bits in
this case.

Finally, using 63 as the cover-it-all shift value is invalid on 32bit,
since pdx values are unsigned long.

Signed-off-by: Jan Beulich <jbeulich@novell.com>