Merge adf_device into graphics_device

As of sepolicy commit a16a59e2
(https://android-review.googlesource.com/94580), adf_device
and graphics_device have the exact same security properties.

Merge them into one type to avoid a proliferation of SELinux
types.

Change-Id: Ib1a24f5d880798600e103b9e14934e41abb1ef95