watchdog: renesas_wdt: Convert to DEFINE_SIMPLE_DEV_PM_OPS()

Convert the Renesas WDT watchdog driver from SIMPLE_DEV_PM_OPS() to
DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr().  This lets us drop the
__maybe_unused annotations from its suspend and resume callbacks, and
reduces kernel size in case CONFIG_PM or CONFIG_PM_SLEEP is disabled.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/3d6d46ff56c908880a167ffb2a74c713060a1a57.1752088043.git.geert+renesas@glider.be


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>