V4L/DVB (8951): xc5000: dont pass devptr in xc5000_attach()

Dont pass devptr in xc5000_attach, dont store it in xc5000_priv.
This pointer is passed into the tuner_callback function, which always
expects a pointer to fe->dvb->priv or i2c_adapter->algo_data.

This prevents future possible bugs in new drivers, such as using a "devptr"
other that the standard fe->dvb->priv in a DVB driver.

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>