media: dvb-frontends/Kconfig: move the SP2 driver to the CI section

The CIMaX SP2 driver is a EN50221 CI controller I2C driver similar to the
cxd2099 driver. Move it's Kconfig block into the newly introduced CI
subsection.

Cc: Olli Salonen <olli.salonen@iki.fi>
Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>