drm/rockchip: vop: Add timeout for DSP hold

If hardware is malfunctioning (e.g., misconfigured clocks?), we can get
stuck here forever, holding various DRM locks and eventually locking up
the entire system. It's better to complain loudly and move on, than to
lock up the system.

In local tests, this operation takes less than 20ms.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20211008153102.1.I2a5dbaaada35023a9703a8db7af501528fbb6e31@changeid