thermal: stm32: fix spelling mistake "preprare" -> "prepare"

There is a spelling mistake in a dev_err error message. Fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200130100537.18069-1-colin.king@canonical.com

drivers/thermal/st/stm_thermal.c

@@ -535,7 +535,7 @@ static int stm_thermal_probe(struct platform_device *pdev)
 	/* Configure and enable HW sensor */
 	ret = stm_thermal_prepare(sensor);
 	if (ret) {
-		dev_err(&pdev->dev, "Error preprare sensor: %d\n", ret);
+		dev_err(&pdev->dev, "Error prepare sensor: %d\n", ret);
 		return ret;
 	}