hwmon: (pmbus/ltc2978) add support for ltc7841

hwmon: (pmbus/ltc2978) add support for ltc7841

Add support for LTC7841. The LTC7841 is a high performance
PolyPhase® single output synchronous boost converter controller.
Multiphase operation reduces input and output capacitor
requirements and allows the use of smaller inductors than the
single-phase equivalent.

The relevant registers in the LTC7841 are similar to the
LTC7880, only reduced by some amount. So it's just a matter of adding
the chip id. The device also doesn't support polling, on top of the
reduced register set, so a separate case for setting the chip info is
added.

Signed-off-by: Mariel Tinaco <Mariel.Tinaco@analog.com>
Message-ID: <20241029013734.293024-4-Mariel.Tinaco@analog.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>