powerpc/mm: fix ".__node_distance" undefined

powerpc/mm: fix ".__node_distance" undefined

  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  ...
  Building modules, stage 2.
WARNING: 1 bad relocations
c0000000013d6a30 R_PPC64_ADDR64    uprobes_fetch_type_table
  WRAP    arch/powerpc/boot/zImage.pseries
  WRAP    arch/powerpc/boot/zImage.epapr
  MODPOST 1849 modules
ERROR: ".__node_distance" [drivers/block/nvme.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2
make: *** Waiting for unfinished jobs....

The reason is symbol "__node_distance" not been exported in powerpc.

Signed-off-by: Mike Qiu <[email protected]>
Acked-by: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Nathan Fontenot <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Srivatsa S. Bhat <[email protected]>
Cc: Jesse Larrew <[email protected]>
Cc: Robert Jennings <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Mike Qiu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>