Add aosp_arm_64b_ab product

Some 32-bit legacy Pi devices use 64-bit binder interface so they can
share the same (usually 64-bit) kernel with newly launched Pi devices,
which require 64-bit binder interface.

Bug: 110497005
Test: $ lunch aosp_arm_64b_ab; m -j
Change-Id: If9f9e2df1ee2f4c25ab6899a47246237721aff02
Merged-In: If9f9e2df1ee2f4c25ab6899a47246237721aff02
(cherry picked from commit a1b30b4a5c3dab35d6bb7759da01a4957add14c0)