libadf: delete libadf & libadfhwc

libadf is a helper library for adf (android display framework)
kernel drivers. The last Android Common Kernel to support adf was
4.4. Delete this helper library since we do not support any kernels
that can use it.

If a vendor needs this library, they can fork it.

If you have any concerns, please contact adelva@google.com.

Bug: 150467766
Test: Compiles
Change-Id: Ib6e1ce2db016e97a165a59b28b9fab5e3ef8f255
Merged-In: Ib6e1ce2db016e97a165a59b28b9fab5e3ef8f255