drm/omap: dss: Make use of the helper macro SET_RUNTIME_PM_OPS()

drm/omap: dss: Make use of the helper macro SET_RUNTIME_PM_OPS()

Use the helper macro SET_RUNTIME_PM_OPS() instead of the verbose
operators ".runtime_suspend/.runtime_resume", because the
SET_RUNTIME_PM_OPS() is a nice helper macro that could be brought
in to make code a little clearer, a little more concise.

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210828084811.104-1-caihuoqing@baidu.com