hwmon: (it87) Add controls for chips with only 4 PWMs

Add feature and support for chips with only 4 PWMs.

Signed-off-by: Frank Crawford <frank@crawford.emu.id.au>
Link: https://lore.kernel.org/r/20230429115205.1547251-3-frank@crawford.emu.id.au


Signed-off-by: Guenter Roeck <linux@roeck-us.net>