ASoC: doc: Fix undefined SND_SOC_DAPM_NOPM argument

[ Upstream commit 67c7666fe808c3a7af3cc6f9d0a3dd3acfd26115 ]

The virtual widget example makes use of an undefined SND_SOC_DAPM_NOPM
argument passed to SND_SOC_DAPM_MIXER().  Replace with the correct
SND_SOC_NOPM definition.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://lore.kernel.org/r/20231121120751.77355-1-cristian.ciocaltea@collabora.com


Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>