doc-rst: audio: re-add captions for the examples

The captions were lost during the format conversion.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/linux_tv/media/v4l/audio.rst

@@ -55,6 +55,7 @@ the :ref:`VIDIOC_QUERYCAP` ioctl.
 
 
 .. code-block:: c
+    :caption: Example 3: Information about the current audio input
 
     struct v4l2_audio audio;
 
@@ -69,6 +70,7 @@ the :ref:`VIDIOC_QUERYCAP` ioctl.
 
 
 .. code-block:: c
+    :caption: Example 4: Switching to the first audio input
 
     struct v4l2_audio audio;