[Driver] Add openSuse AArch64 Triple

Summary:
openSuse has AArch64 support, with images running on the Raspberry Pi 3.
The libraries and headers live under the aarch64-suse-linux subdirectory,
which is currently not in the AArch64 triples list. Address this by adding
the corresponding string to AArch64Triples.

Reviewers: chandlerc, bruno, bkramer, rengolin

Subscribers: aemerson, rengolin, cfe-commits

Differential Revision: https://reviews.llvm.org/D28238

llvm-svn: 291598