The last user of dvb_pll_configure was the dvb-usb function
dvb_usb_tuner_calc_regs(), which was nothing more than a wrapper around
dvb_pll_configure().  It's just a copy of the functionality provided by
the tuner_ops calc_regs method, and can be deleted.

There were two users of dvb_usb_tuner_calc_regs().
One was dvb_usb_tuner_set_params_i2c(), which is converted to use
fe->ops.tuner_ops.calc_regs().

The other was the digitv driver.  This driver can use one of two demods,
mt352 or nxt6000.  

For the mt352, the driver would set tuner_ops.calc_regs to 
dvb_usb_tuner_calc_regs().  

We can just attach dvb_pll and use the tuner_ops.calc_regs() provided by 
that module. For the nxt600, the driver would set tuner_ops.set_params 
to digitv_nxt6000_tuner_set_params.  

That function would in turn use dvb_usb_tuner_calc_regs().

We convert it to use tuner_ops.calc_regs() instead, and use 
dvb_pll_attach.

The digitv_tuner_attach() needs to know which frontend was attached by 
digitv_frontend_attach(), since the nxt6000 needs tuner_ops.set_params() 
to be overridden with digitv_nxt6000_tuner_set_params().

So, to do this a digitv_state that says which frontend was used is added 
to the dvb_usb_device private state field.
Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>