Use the new DEFINE_DRM_MODE_CONFIG_HELPER_PM_OPS() macro to create a
"struct dev_pm_ops" that can be used by this driver, instead of using
custom PM callbacks with the same behaviour.
v2: Use the DEFINE_DRM_MODE_CONFIG_HELPER_PM_OPS() macro instead of an
exported dev_pm_ops.
Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>