regulator: virtual: warn against production use

This driver is only meant for debugging and testing. Currently, it's
not possible to use it without patching the kernel since it requires
platform data, but we'll be adding devicetree support, so add a loud
warning to make it clear that it's still only meant for debugging and
testing.

Signed-off-by: Vincent Whitchurch <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/virtual.c

···
 {
 	char *reg_id = dev_get_platdata(&pdev->dev);
 	struct virtual_consumer_data *drvdata;
+	static bool warned;
 	int ret;
+
+	if (!warned) {
+		warned = true;
+		pr_warn("**********************************************************\n");
+		pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
+		pr_warn("**                                                      **\n");
+		pr_warn("** regulator-virtual-consumer is only for testing and   **\n");
+		pr_warn("** debugging.  Do not use it in a production kernel.    **\n");
+		pr_warn("**                                                      **\n");
+		pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
+		pr_warn("**********************************************************\n");
+	}
 
 	drvdata = devm_kzalloc(&pdev->dev, sizeof(struct virtual_consumer_data),
 			       GFP_KERNEL);