driver core: cpu: Make cpu_show_not_affected() static

Fix a -Wmissing-prototypes warning and add the gather_data_sampling()
stub macro call for real.

Fixes: 0fddfe33

 ("driver core: cpu: Unify redundant silly stubs")
Closes: https://lore.kernel.org/oe-kbuild-all/202308101956.oRj1ls7s-lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/202308101956.oRj1ls7s-lkp@intel.com