libqservice: Defer enabling partial update PP turns off

When client prefer to enable PU(partial update) over PP(post
processing), delay enabling PU until PP turns off its
features completely. This change introduces hand shaking flags
between PP and HWC through binder calls. When requested to turn
on PU, we notify PP through the sys_fs node. When PP is done
shutting off it features, it acknowledges back to HWC to actually
turn on PU.

Change-Id: I72008f2313b93497f55c0435367ef62cd772c2c4
4 files changed