hwmon: (ibmpowernv) Fix label for cores numbers not threads

Currently the label says "Core" but lists the thread numbers. This
ends up looking like this:
    # cat /sys/class/hwmon/hwmon0/temp[1-4]_label
    Core 0-7
    Core 8-15
    Core 16-23
    Core 24-31

This is misleading as it looks like it's cores 0-7 when it's actually
threads 0-7.

This changes the print to just give the core number, so the output now
looks like this:
    # cat /sys/class/hwmon/hwmon0/temp[1-4]_label
    Core 0
    Core 8
    Core 16
    Core 24

Signed-off-by: Michael Neuling <mikey@neuling.org>
Acked-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>