clocksource/drivers/ingenic-timer: Use pm_sleep_ptr() macro

The use of the pm_sleep_ptr() macro allows the compiler to always see
the dev_pm_ops structure and related functions, while still allowing the
unused code to be removed, without the need for the __maybe_unused
markings.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20230618153937.96649-1-paul@crapouillou.net