[AMDGPU] Implement infrastructure to set options in AMDGPUToolChain

In current OpenCL implementation some options are set in OpenCL RT/Driver, which causes discrepancy between online and offline paths.
Implement infrastructure to move options from OpenCL RT/Driver to AMDGPUToolChain using overloaded TranslateArgs() method.
Create map for default options values, as Options.td doesn't support default values (in contrast with OPTIONS.def).
Add two driver options: -On and -mNN (like -O3, -m64).
Some minor formatting changes to follow the clang-format style.

Differential Revision: https://reviews.llvm.org/D37386

llvm-svn: 312524