ASoC: cs42l73: Fix mask bits for SOC_VALUE_ENUM_SINGLE

commit 1555b652970e541fa1cb80c61ffc696bbfb92bb7 upstream.

The mask bits values were wrong for the SOC_VALUE_ENUM_SINGLE for the mono mix controls.

Reported-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Brian Austin <brian.austin@cirrus.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>