DVB: fix dvb_pll_attach for mt352/zl10353 in cx88-dvb, and nxt200x

Typical wiring of MT352, ZL10353, NXT2002 and NXT2004 based tuners
differ from dvb-pll's expectation that the PLL is directly accessible.
On these boards, the PLL is actually hidden behind the demodulator, and
as such can only be accessed via the demodulator's interface.  It was
failing to communicate with the PLL during an attach test and
subsequently not connecting the tuner ops.

By passing a NULL I2C bus handle to dvb_pll_attach, this accessibility
check can be bypassed.  Do this for the affected boards.  Also fix a
possible NULL dereference at sleep time, which would otherwise be
exposed by this change.

This patch has been backported to the 2.6.18.y stable kernel series
from the original changesets from Chris Pascoe and Michael Krufky,
already present in the upstream 2.6.19 kernel tree.
Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>