drm: exynos: Remove #ifdef guards for PM related functions

Use the DEFINE_RUNTIME_DEV_PM_OPS(), SYSTEM_SLEEP_PM_OPS(),
RUNTIME_PM_OPS() and pm_ptr() macros to handle the runtime and suspend
PM callbacks.

These macros allow the suspend and resume functions to be automatically
dropped by the compiler when CONFIG_PM is 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: Inki Dae <inki.dae@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221129191733.137897-10-paul@crapouillou.net