drm/rockchip: Remove analogix psr worker

Now that the spinlocks and timers are gone, we can remove the psr
worker located in rockchip's analogix driver and do the enable/disable
directly. This should simplify the code and remove races on disable.

Cc: 征增 王 <wzz@rock-chips.com>
Cc: Stéphane Marchesin <marcheu@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20180309222327.18689-3-enric.balletbo@collabora.com