Instead of using timer and spinlocks, use delayed_work and
mutexes for rockchip psr. This allows us to make blocking
calls when enabling/disabling psr (which is sort of important
given we're talking over dpcd to the display).

Cc: Caesar Wang <wxt@rock-chips.com>
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/20180305222324.5872-3-enric.balletbo@collabora.com