media: admin-guide/pixfmt-meta-rkisp1.rst: pixfmt reference conforming with macro

Fix warnings from make htmlddocs:

Documentation/output/videodev2.h.rst:6: WARNING: undefined label: v4l2-meta-fmt-rk-isp1-params (if the link has no caption the label must precede a section header)
Documentation/output/videodev2.h.rst:6: WARNING: undefined label: v4l2-meta-fmt-rk-isp1-stat-3a (if the link has no caption the label must precede a section header)

Fixes: df22026a

 ("media: videodev2.h, v4l2-ioctl: add rkisp1 meta buffer format")
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>