Annotate pnp_ids as '__used' to fix following warning:

  CC      drivers/platform/x86/fujitsu-laptop.o
drivers/platform/x86/fujitsu-laptop.c:1243: warning: ‘pnp_ids’ defined but not used
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NMatthew Garrett <mjg@redhat.com>