don't automatically unblank external displays

this should be handled by the display-manager. we were doing
that in SF because until recently we didn't have enough support
in the HAL. however, this is now causing other problems when
plugging hdmi while the screen is off for instance.

Bug: 7150885
Change-Id: I739b209056a765d38d05295cf202f67ee0f506ae
1 file changed