Remove NN canonical IDevice::isUpdatable -- hal

This CL alters the AIDL utility "getDevices" to return whether or not a
service is updatable. This CL additional removes IDevice::isUpdatable
because it is now redundant with the changes to "getDevices".

Bug: 170696350
Test: mma
Test: NeuralNetworksTest_static
Change-Id: I86228763937c0dd2ee5b1d9d547c367cd7504ed4