x86/platform/uv: Make uv_pcibus_kset and uv_hubs_kset static

Fix the following sparse warnings:

  drivers/platform/x86/uv_sysfs.c:22:13: warning: symbol \
	  'uv_pcibus_kset' was not declared. Should it be static?
  drivers/platform/x86/uv_sysfs.c:23:13: warning: symbol \
	  'uv_hubs_kset' was not declared. Should it be static?

Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lkml.kernel.org/r/1606734713-43919-1-git-send-email-zou_wei@huawei.com