drm/ssd130x: Print the PWM's label instead of its number

struct pwm_device::pwm is a write-only variable in the pwm core and used
nowhere apart from this and another dev_dbg. So it isn't useful to
identify the used PWM. Emit the PWM's label instead in the debug
message.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230728145824.616687-2-u.kleine-koenig@pengutronix.de

drivers/gpu/drm/solomon/ssd130x.c

@@ -272,8 +272,8 @@ static int ssd130x_pwm_enable(struct ssd130x_device *ssd130x)
 	/* Enable the PWM */
 	pwm_enable(ssd130x->pwm);
 
-	dev_dbg(dev, "Using PWM%d with a %lluns period.\n",
-		ssd130x->pwm->pwm, pwm_get_period(ssd130x->pwm));
+	dev_dbg(dev, "Using PWM %s with a %lluns period.\n",
+		ssd130x->pwm->label, pwm_get_period(ssd130x->pwm));
 
 	return 0;
 }