V4L/DVB (4191): Add CX2341X MPEG encoder module.

Adds the cx2341x.c module that handles the programming of the Conexant
cx23415/6 MPEG encoder chip used by cx88-blackbird, pvrusb2 and ivtv.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>