amd: Don't handle nir_tex_src_ms_mcs

It's an intel-specific texture source and will never be seen on AMD.

Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11775>

src/amd/llvm/ac_nir_to_llvm.c

@@ -4331,8 +4331,6 @@ static void visit_tex(struct ac_nir_context *ctx, nir_tex_instr *instr)
       case nir_tex_src_ms_index:
          sample_index = get_src(ctx, instr->src[i].src);
          break;
-      case nir_tex_src_ms_mcs:
-         break;
       case nir_tex_src_ddx:
          ddx = get_src(ctx, instr->src[i].src);
          args.g16 = instr->src[i].src.ssa->bit_size == 16;

src/gallium/drivers/r600/sfn/sfn_emittexinstruction.cpp

@@ -586,7 +586,6 @@ bool EmitTexInstruction::get_inputs(const nir_tex_instr& instr, TexInputs &src)
       case nir_tex_src_plane:
       case nir_tex_src_projector:
       case nir_tex_src_min_lod:
-      case nir_tex_src_ms_mcs:
       default:
          sfn_log << SfnLog::tex << "Texture source type " <<  instr.src[i].src_type << " not supported\n";
          retval = false;