x86_64: various cleanups in NUMA scan node

In acpi_scan_nodes(), we immediately return -1 if acpi_numa <= 0, meaning
we haven't detected any underlying ACPI topology or we have explicitly
disabled its use from the command-line with numa=noacpi.

acpi_table_print_srat_entry() and acpi_table_parse_srat() are only
referenced within drivers/acpi/numa.c, so we can mark them as static and
remove their prototypes from the header file.

Likewise, pxm_to_node_map[] and node_to_pxm_map[] are only used within
drivers/acpi/numa.c, so we mark them as static and remove their externs
from the header file.

The automatic 'result' variable is unused in acpi_numa_init(), so it's
removed.

Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>