Rename 'Mono DAC Playback Volume' to 'DAC2 Playback Volume' and move it
from rt5640_specific_snd_controls[] to rt5640_snd_controls[].

The RT5640_DAC2_DIG_VOL register controlled by this mixer-element has
nothing to do with the Mono (Amplified) output which is only available
on the ALC5640 chip and not on the ALC5642 chip.

The RT5640_DAC2_DIG_VOL volume-control is the main volume control for
audio coming from the I2S2 / AIF2 input of the chip and as such is also
available on the ALC5642.

This commit results in the following userspace visible changes:

1. On devices with an ACL5640 codec, the 'Mono DAC Playback Volume'
control is renamed to 'DAC2 Playback Volume' allowing the alsa-lib
mixer code to properly group it with the 'DAC2 Playback Switch' which
is controlling the mute bits in the RT5640_DAC2_DIG_VOL register.

Note the removal of the 'Mono DAC Playback Volume' is not an issue for
userspace because the UCM profiles do not use it (the UCM profiles are
shared betweent the 5640 and 5642 and only the 5640 had this control).

2. On devices with an ACL5642 codec, there now will be a new
'DAC2 Playback Volume', grouped with the 'DAC2 Playback Switch'

Having a complete 'DAC2 Playback Volume' / 'DAC2 Playback Switch' pair
on both variants will allow enabling hardware-volume control by
setting the UCM PlaybackMasterElem to "DAC2" on devices where the
I2S2/AIF2 interface of the codec is used.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210307150503.34906-2-hdegoede@redhat.comSigned-off-by: Mark Brown <broonie@kernel.org>