drm/rockchip: analogix_dp: add runtime PM handling

Hook up the runtime PM suspend/resume paths to make the rockchip
glue behave more like the exynos one. The same suspend/resume
functions are used for system sleep via the runtime PM force
suspend/resume.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240619182200.3752465-2-l.stach@pengutronix.de