[ALSA] snd-bt87x: Improve support for different board types

[ALSA] snd-bt87x: Improve support for different board types

Different cards have different audio configurations, but the driver didn't
support this.  The only setting it had was the digital rate.
This patch adds a board configuration list.  Currently, configurable items are
the digital rate and the digital data format (for cards with an external ADC),
a flag for the absence of an external ADC, and a flag for no connection to the
Bt87x internal ADC.
This allows cards that don't use the internal ADC to omit the ALSA 'Bt87x
analog' device and related controls.  Cards without an external ADC can omit
the 'Bt87x digital' device.
In order to support the CS5331A ADC used on the Osprey 440 and 2x0 cards, the
digital format needs to be different than the default.
Support could be added for defining:
  The connections or lack of them to the Bt87x's internal ADC mux
  Multiple sample rates for an external ADC (e.g. Osprey)
  Control of an external mux for an external ADC (e.g. Osprey)
The card definitions for cards other than the Ospreys are kept equivalent to
their old values.  This is likely inaccurate for most cards, as it is doubtful
that both an external and the internal ADC would be used.  Lacking information
on those cards, the behavior is left unchanged.

Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>