sepolicy: rework ashmem_device permissions

Only allow apps targetting < Q and ephemeral apps to open /dev/ashmem.
Ephemeral apps are not distinguishable based on target API. So allow
ephemeral_app to open /dev/ashmem for compatibility reasons.

For sake of simplicity, allow all domains /dev/ashmem permissions other
than "open". Reason being that once we can remove "open" access
everywhere, we can remove the device altogether along with  other
permission.

Bug: 134434505
Test: boot crosshatch; browse internet, take picture;
no ashmem_device denials
Change-Id: Ib4dddc47fcafb2697795538cdf055f305fa77799
6 files changed