media: ext-ctrls-codec-stateless.rst: fix an H-264 table format

The Picture Parameter Set Flags table for H-264 doesn't output
well on PDF. There are missing format instructions for LaTeX, and
the columns are too long.

Reduce the size of the second column, as 16 bits is more than enough
for the current flags usage, and add the needed bits for it to be
properly output in PDF format.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>