media: ext-ctrls-codec.rst: fix indentation

media: ext-ctrls-codec.rst: fix indentation

The indentation was wrong, causing the documentation build to
fail with:

Sphinx parallel build error:
docutils.utils.SystemMessagePropagation: <system_message level="3" line="1202" source="/home/hans/work/src/v4l/media-git/Documentation/media/userspace-api/v4l/ext-ctrls-codec.rst"
type="ERROR"><paragraph>Error parsing content block for the "flat-table" directive: two-level bullet list expected, but row 1 does not contain a second-level bullet list.</paragraph><literal_block
xml:space="preserve">.. flat-table::
    :header-rows:  0
    :stub-columns: 0

    * - ``V4L2_MPEG_VIDEO_INTRA_REFRESH_PERIOD_TYPE_RANDOM``
      - The whole frame is completely refreshed randomly
      after the specified period.
    * - ``V4L2_MPEG_VIDEO_INTRA_REFRESH_PERIOD_TYPE_CYCLIC``
      - The whole frame MBs are completely refreshed in cyclic order
      after the specified period.

</literal_block></system_message>
make[1]: *** [Documentation/Makefile:96: htmldocs] Error 2
make: *** [Makefile:1678: htmldocs] Error 2

Link: https://lore.kernel.org/linux-media/62b53cbb-f3e2-ed8a-bba2-3f4145d9b8db@xs4all.nl
Fixes: 72d8e98ef8fd ("media: v4l2-ctrls: Add intra-refresh type control")
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>