mfd: intel_soc_pmic_chtdc_ti: Switch from __maybe_unused to pm_sleep_ptr() etc

mfd: intel_soc_pmic_chtdc_ti: Switch from __maybe_unused to pm_sleep_ptr() etc

Letting the compiler remove these functions when the kernel is built
without CONFIG_PM_SLEEP support is simpler and less heavier for builds
than the use of __maybe_unused attributes.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220906134256.14293-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Lee Jones <lee@kernel.org>