hwmon: (adt7475) Add support for Imon readout on ADT7490

Add support for the ADT7490's Imon voltage readout. It is handled
largely the same way as the existing Vtt readout.

Signed-off-by: Timothy Pearson <tpearson@raptorengineering.com>
Co-developed-by: Shawn Anastasio <sanastasio@raptorengineering.com>
Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com>
Link: https://lore.kernel.org/r/20230914223947.829025-1-tpearson@raptorengineering.com


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