ASoC: dapm: Lock during userspace access

The DAPM lock must be held when accessing the DAPM graph status through
sysfs or debugfs, otherwise concurrent changes to the graph can result in
undefined behaviour.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org