staging: greybus: simplify getting .drvdata

We should get drvdata from struct device directly. Going via
platform_device is an unneeded step back and forth.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/arche-platform.c

@@ -315,8 +315,7 @@ static ssize_t state_store(struct device *dev,
 			   struct device_attribute *attr,
 			   const char *buf, size_t count)
 {
-	struct platform_device *pdev = to_platform_device(dev);
-	struct arche_platform_drvdata *arche_pdata = platform_get_drvdata(pdev);
+	struct arche_platform_drvdata *arche_pdata = dev_get_drvdata(dev);
 	int ret = 0;
 
 	mutex_lock(&arche_pdata->platform_state_mutex);