[AMDGPU] New 64 bit div/rem expansion

Old expansion was 20 VGPRs, 78 SGPRs and ~380 instructions.
This expansion is 11 VGPRs, 12 SGPRs and ~120 instructions.

Passes OpenCL conformance test_integer_ops quick_[u]long_math

Differential Revision: https://reviews.llvm.org/D38607

llvm-svn: 315081