i2c: kempld: Convert to use regular device PM

i2c: kempld: Convert to use regular device PM

Provide PM callbacks through platform_driver.driver.pm instead of
platform_driver.{suspend,resume} as any good-behaved driver should do.

Use the new PM macros for the suspend and resume functions to be
automatically dropped by the compiler when CONFIG_PM or
CONFIG_PM_SLEEP are disabled, without having to use #ifdef guards.

This has the advantage of always compiling these functions in,
independently of any Kconfig option. Thanks to that, bugs and other
regressions are subsequently easier to catch.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20230722115046.27323-11-paul@crapouillou.net
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>