Find7: fix framebuffer sysfs node permissions

MDP idle time notifier is used by our new display HAL.
Although we don't have HDMI support via native hardware ports,
we still want fb1 node permissions to allow HDMI usecases,
especially to accomodate for MHL USB usecases for externel displays.

Change-Id: I7d541de7e063d749a0681884af15e3b6bb35bb3d