AMDGPU: Force inlining if LDS global address is used

AMDGPU: Force inlining if LDS global address is used

These won't work for the forseeable future. These aren't allowed
from OpenCL, but IPO optimizations can make them appear.

Also directly set the attributes on functions, regardless
of the linkage rather than cloning functions like before.

llvm-svn: 336587