intel/compiler: Add some restrictions to MOV_INDIRECT and BROADCAST

These restrictions effectively already existed due to the way we use
indirect sources but weren't being directly enforced.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/intel/compiler/brw_shader.cpp

@@ -851,6 +851,8 @@ backend_instruction::can_do_source_mods() const
    case BRW_OPCODE_FBH:
    case BRW_OPCODE_FBL:
    case BRW_OPCODE_SUBB:
+   case SHADER_OPCODE_BROADCAST:
+   case SHADER_OPCODE_MOV_INDIRECT:
       return false;
    default:
       return true;