[AMDGPU] fixes for lds f32 builtins

1. added restrictions to memory scope, order and volatile parameters
2. added custom processing for these builtins - currently is not used code,
   needed to switch off GCCBuiltin link to the builtins (ongoing change to llvm
   tree)
3. builtins renamed as requested

Differential Revision: https://reviews.llvm.org/D43281

llvm-svn: 332848