Add support for Myriad ma2x8x series of CPUs

Summary:
Also:
- Add support for some older Myriad CPUs that were missing.
- Fix some incorrect compiler defines for exisitng CPUs.

Reviewers: jyknight

Subscribers: fedor.sergeev

Differential Revision: https://reviews.llvm.org/D37551

llvm-svn: 314706