doc-rst: linux_tv: Fix remaining undefined references

doc-rst: linux_tv: Fix remaining undefined references

Fix Sphinx those warnings:
	WARNING: undefined label: fdl-modified>`as given on the :ref:`title page <fdl-title-page (if the link has no caption the label must precede a section header)
	WARNING: undefined label: v4l2-pix-fmt-yuv420 (if the link has no caption the label must precede a section $
	WARNING: undefined label: pixfmt-srggb10 (if the link has no caption the label must precede a section heade$

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>