x86: Set hotpluggable nodes in nodes_possible_map

nodes_possible_map does not currently include nodes that have SRAT
entries that are all ACPI_SRAT_MEM_HOT_PLUGGABLE since the bit is
cleared in nodes_parsed if it does not have an online address range.

Unequivocally setting the bit in nodes_parsed is insufficient since
existing code, such as acpi_get_nodes(), assumes all nodes in the map
have online address ranges.  In fact, all code using nodes_parsed
assumes such nodes represent an address range of online memory.

nodes_possible_map is created by unioning nodes_parsed and
cpu_nodes_parsed; the former represents nodes with online memory and
the latter represents memoryless nodes.  We now set the bit for
hotpluggable nodes in cpu_nodes_parsed so that it also gets set in
nodes_possible_map.

[ hpa: Haicheng Li points out that this makes the naming of the
  variable cpu_nodes_parsed somewhat counterintuitive.  However, leave
  it as is in the interest of keeping the pure bug fix patch small. ]

Signed-off-by: David Rientjes <rientjes@google.com>
Tested-by: Haicheng Li <haicheng.li@linux.intel.com>
LKML-Reference: <alpine.DEB.2.00.1001201152040.30528@chino.kir.corp.google.com>
Cc: <stable@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>