[AMDGPU][MC][DOC] Updated AMD GPU assembler description

Stage 2: added detailed description of operands

See bug 36572: https://bugs.llvm.org/show_bug.cgi?id=36572

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349368 91177308-0d34-0410-b5e6-96231b3b80d8
279 files changed