Add support for openSUSE RISC-V triple

Reviewers: asb

Reviewed By: asb

Subscribers: lenary, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, zzheng, edward-jones, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, lebedev.ri, kito-cheng, shiva0217, rogfer01, dexonsmith, rkruppe, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D63497

Patch by Andreas Schwab (schwab)

llvm-svn: 367565