media: v4l: vidioc-prepare-buf.rst: fix link to VIDIOC_QBUF

The description for VIDIOC_PREPARE_BUF results in the following
sentence: "...before actually enqueuing it, using the ioctl VIDIOC_QBUF,
VIDIOC_DQBUF ioctl...".

The intent is to only refer to VIDIOC_QBUF though, so fix this.
Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/media/uapi/v4l/vidioc-prepare-buf.rst

@@ -34,7 +34,7 @@ Description
 
 Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to
 pass ownership of the buffer to the driver before actually enqueuing it,
-using the :ref:`VIDIOC_QBUF` ioctl, and to prepare it for future I/O. Such
+using the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl, and to prepare it for future I/O. Such
 preparations may include cache invalidation or cleaning. Performing them
 in advance saves time during the actual I/O. In case such cache
 operations are not required, the application can use one of