doc-rst: v4l/pixfmt: re-join a broken paragraph

Originally, at the DocBook, the "Byte Order" were a single
paragraph with the string that follows it. The conversion
broke it, and, sometimes, it added an extra dot.

Fix them altogheter at pixfmt-*.

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