soc: qcom: llcc: Handle a second device without data corruption

Usually there is only one llcc device. But if there were a second, even
a failed probe call would modify the global drv_data pointer. So check
if drv_data is valid before overwriting it.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Fixes: a3134fb0 ("drivers: soc: Add LLCC driver")
Link: https://lore.kernel.org/r/20230926083229.2073890-1-u.kleine-koenig@pengutronix.deSigned-off-by: Bjorn Andersson <andersson@kernel.org>

drivers/soc/qcom/llcc-qcom.c

@@ -1120,6 +1120,9 @@ static int qcom_llcc_probe(struct platform_device *pdev)
 	u32 version;
 	struct regmap *regmap;
 
+	if (!IS_ERR(drv_data))
+		return -EBUSY;
+
 	drv_data = devm_kzalloc(dev, sizeof(*drv_data), GFP_KERNEL);
 	if (!drv_data) {
 		ret = -ENOMEM;