hwmon: (occ) Fix power sensor indexing

In the case of power sensor version 0xA0, the sensor indexing overlapped
with the "caps" power sensors, resulting in probe failure and kernel
warnings. Fix this by specifying the next index for each power sensor
version.

Fixes: 54076cb3 ("hwmon (occ): Add sensor attributes and register ...")
Cc: stable@vger.kernel.org
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Tested-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>