Use dev_pm_ops instead of the deprecated legacy suspend/resume callbacks.

Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Anton Vorontsov <anton@enomsg.org>