[media] i2c: Remove obsolete cleanup for clientdata

A few new i2c-drivers came into the kernel which clear the clientdata-pointer
on exit. This is obsolete meanwhile, so fix it and hope the word will spread.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>