framework-wifi: clean up AIDL exports (Attempt 2)

Remove AIDL exports to not leak internal
implementation as AIDL is not an official API
of the Wifi module.

Previous attempt broke the build.

Bug: 147757606
Change-Id: I2edeeccf83b9460881c5d4ccc6bd5d6e3befa700
Test: compiles
2 files changed