ALSA: pcm: Introduce MSBITS subformat interface

Improve granularity of format selection for S32/U32 formats by adding
constants representing 20, 24 and MAX most significant bits.

The MAX means the maximum number of significant bits which can
the physical format hold. For 32-bit formats, MAX is related
to 32 bits. For 8-bit formats, MAX is related to 8 bits etc.

As there is only one user currently (format S32_LE), subformat is
represented by a simple u32 and stores flags only for that one user
alone. The approach of subformat being part of struct snd_pcm_hardware
is a compromise between ALSA and ASoC allowing for
hw_params-intersection code to be alloc/free-less while not adding any
new responsibilities to ASoC runtime structures.

Acked-by: Mark Brown <[email protected]>
Signed-off-by: Jaroslav Kysela <[email protected]>
Co-developed-by: Cezary Rojewski <[email protected]>
Signed-off-by: Cezary Rojewski <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>

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