ASoC: max9867: fix volume controls

ASoC: max9867: fix volume controls

commit 8ba4dc3cff8cbe2c571063a5fd7116e8bde563ca upstream.

The xmax values for Master Playback Volume and Mic Boost
Capture Volume are specified incorrectly (one greater)
which results in the wrong dB gain being shown to the user
in the case of Master Playback Volume.

Signed-off-by: Pavel Dobias <dobias@2n.cz>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200515120757.24669-1-dobias@2n.cz
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>