add module_arm64only product

64bit only systems won't load modules with mixed 32/64 binaries. We need
a 64bit only product to build with.

Bug: 205990590
Test: lunch module_arm64only && m
Change-Id: I050a673bfa95978e624e64004089fe7a2b8e0a95
Merged-In: I050a673bfa95978e624e64004089fe7a2b8e0a95