ASoC: codecs: peb2466: Change the +/- 6dB switch to a volume

ASoC: codecs: peb2466: Change the +/- 6dB switch to a volume

In addition to the digital volume adjustment, infineon peb2466 codec
has an analog adjustment which can be set to either 0dB or +/-6dB.
At the time being it is defined as a switch and appears in 'alsamixer'
like a 'mute'.

This adjustment isn't a mute, change it to a 'volume' with an
associated dB range.

With this change, this adjustment now appears in 'alsamixer' as a
standard volume slider which can have two positions.

Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Acked-by: Herve Codina <herve.codina@bootlin.com>
Link: https://patch.msgid.link/418fe76d1c9efc8182ab57b6b426a8c723e025fe.1773056714.git.chleroy@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>