x86/platform/uv: Update sysfs documentation

Update sysfs documentation file to include moved /proc leaves.

Signed-off-by: Mike Travis <mike.travis@hpe.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lkml.kernel.org/r/20201128034227.120869-6-mike.travis@hpe.com