V4L/DVB (5899): bttv: Fix Viewcast Osprey 440 support

Various gpio and mux settings for the Osprey 440 weren't correct.  Fix them
and provide some documentation about how the gpios work.

The osprey eeprom routine wasn't run for the 440, add it.  It was also crap,
re-written to be better.

Add the Osprey 440 to the Bt878 ALSA driver's whitelist.  Currently the sample
rate is fixed at 32kHz, as the driver doesn't support different rates for
digital input mode, though the card can select the rate from 32, 44.1, or 48
kHz via gpio.

Setting the audio gain via ALSA isn't supported yet; a userspace tool that
programs the X9221 via i2c-dev must be used.

The Bt878 digital audio format isn't programmed correctly for the CS5331A ADC
used, resulting in extremely garbled sound.  That is fixed in a followup
patch.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>