linux-phytec-ti

[media] doc-rst: fix a missing reference for V4L2_BUF_FLAG_LAST

Fix it by adding a header to the flat-table to match to
the list of define symbols.

As a side-effect, it also removes some exceptions from
videodev2.h.rst.

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