V4L/DVB (6466): v4l2-i2c-drv: first call remove, then detach client

The remove driver function expects that the client is still attached
to the driver, so do the detach after calling remove().

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