The setting of vop registers need a reg_done writing to take effect.
In vop_enable the vop return to work by by restoring registers, but the
registers do not take effect immediately, it should a vop_cfg_done
after it. The same thing is needed by windows_disabled in
vop_crtc_disable.
Signed-off-by: Chris Zhong <zyw@rock-chips.com>