i2c: omap: switch to NOIRQ_SYSTEM_SLEEP_PM_OPS() and RUNTIME_PM_OPS()

Replace SET_NOIRQ_SYSTEM_SLEEP_PM_OPS() and SET_RUNTIME_PM_OPS() by
NOIRQ_SYSTEM_SLEEP_PM_OPS() and RUNTIME_PM_OPS().
The usage of pm_ptr() and these more recent macros allows the compiler to
see and drop the dead code.
The unnecessary '__maybe_unused' annotations on PM functions can be
removed.

Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>