ASoC: wm8958: Move DSP firmware lock to driver level

The wm8958 driver uses the snd_soc_codec mutex to protect the various
firmware pointers from concurrent assignment. This patch moves this lock to
the driver level. This will allow us to eventually remove the snd_soc_codec
mutex.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/wm8994.c

@@ -4457,6 +4457,8 @@ static int wm8994_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	platform_set_drvdata(pdev, wm8994);
 
+	mutex_init(&wm8994->fw_lock);
+
 	wm8994->wm8994 = dev_get_drvdata(pdev->dev.parent);
 
 	pm_runtime_enable(&pdev->dev);