ACPI: fix modpost warnings

for sn2_defconfig:

WARNING: vmlinux.o(.text+0x4b8601): Section mismatch: reference to .init.data:node_to_pxm_map (between '__acpi_map_pxm_to_node' and 'acpi_get_pxm')
WARNING: vmlinux.o(.text+0x4b8741): Section mismatch: reference to .init.data:pxm_to_node_map (between 'acpi_map_pxm_to_node' and 'acpi_get_node')

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Len Brown <len.brown@intel.com>