hwmon: (ltc2947) Switch to EXPORT_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr()

These newer PM macros allow the compiler to see what code it can remove
if !CONFIG_PM_SLEEP. This allows the removal of __maybe_unused markings
whilst achieving the same result. In this case it also lets the
structure itself be removed.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20220925172759.3573439-9-jic23@kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

hwmon: Add support for ltc2947

The ltc2947 is a high precision power and energy monitor with an
internal sense resistor supporting up to +/- 30A. Three internal no
Latency ADCs ensure accurate measurement of voltage and current, while
high-bandwidth analog multiplication of voltage and current provides
accurate power measurement in a wide range of applications. Internal or
external clocking options enable precise charge and energy measurements.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20191021154115.319073-1-nuno.sa@analog.com
[groeck: Removed unnecessary checks when reading temperature and energy;
PAGE{0,1} -> LTC2947_PAGE_{0,1}]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>