Input: mpr121-touchkey - switch to DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr()

Input: mpr121-touchkey - switch to DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr()

SIMPLE_DEV_PM_OPS() is deprecated as it requires explicit protection
against unused function warnings.  The new combination of pm_sleep_ptr()
and DEFINE_SIMPLE_DEV_PM_OPS() allows the compiler to see the functions,
thus suppressing the warning, but still allowing the unused code to be
removed. Thus also drop the __maybe_unused markings.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20221204180841.2211588-9-jic23@kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>