hwmon: (lm87) Use hwmon to create the sysfs groups

This is the expected thing for a hwmon driver to do, this changes
the sysfs paths from, say:

  /sys/bus/i2c/devices/0-002c/temp1_input

to:

  /sys/bus/i2c/devices/0-002c/hwmon/hwmon0/temp1_input

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>