libc: fix returned timeout-left value

If the suspend method for the main thread detects that the suspend
condition is false it must return the passed timeout value (not always
0). Otherwise, the caller may incorrectly assume the timeout expired.

repos/libports/src/lib/libc/internal/kernel.h

@@ -291,7 +291,7 @@ struct Libc::Kernel final : Vfs::Io_response_handler,
 			}
 
 			if (!check.suspend() && !_kernel_routine)
-				return 0;
+				return timeout_ms;
 
 			if (timeout_ms > 0)
 				_main_timeout.timeout(timeout_ms);