Fix coroutine disable option

6c97486f has broken this option.  yield_context.hpp is not pulled in if
this option is enabled, so we cannot reference it in that context.

Change-Id: Ife57da50c8341c227efd8fc61d25c37594545660
Signed-off-by: Ed Tanous <edtanous@google.com>
diff --git a/include/sdbusplus/asio/connection.hpp b/include/sdbusplus/asio/connection.hpp
index 8badc94..eed2827 100644
--- a/include/sdbusplus/asio/connection.hpp
+++ b/include/sdbusplus/asio/connection.hpp
@@ -83,8 +83,12 @@
     inline auto async_send(message_t& m, CompletionToken&& token,
                            uint64_t timeout = 0)
     {
+#ifdef SDBUSPLUS_DISABLE_BOOST_COROUTINES
+        constexpr bool is_yield = false;
+#else
         constexpr bool is_yield =
             std::is_same_v<CompletionToken, boost::asio::yield_context>;
+#endif
         using return_t = std::conditional_t<is_yield, message_t, message_t&>;
         using callback_t = void(boost::system::error_code, return_t);
         return boost::asio::async_initiate<CompletionToken, callback_t>(