drm/msm/sde: AD4 feature enhancement

Currently when AD4 feature is enabled for the first time, its strength
will start from some middle range value instead of zero. This change
adds a new startup state to configure the initial strength to start
from zero to avoid undesired strength change.

If user sets the ambient light or backlight or assertiveness
values during the idle power resume(ipcr) state, AD strength will
reach to the target strength in one or two frames due to the ipcr
configuration, which will appear as a sudden change. This change adds
the caching mechanism for ambient light, backlight and assertiveness
during ipcr state, and apply them after state is switched back to run.

CRs-Fixed: 2093305
Change-Id: I7b23d42e6eae009453dda9020c68f5cb47d18bae
Signed-off-by: Ping Li <pingli@codeaurora.org>