chore(light_sensor) make error codes negative, use more precise error number

epicardium/modules/light_sensor.c

@@ -15,7 +15,7 @@ static TaskHandle_t poll_task;
 {
 	const sys_cfg_adc_t sys_adc_cfg = NULL; /* No system specific configuration needed. */
 	if (ADC_Init(0x9, &sys_adc_cfg) != E_NO_ERROR) {
-        return EINVAL;
+        return -EINVAL;
 	}
 	GPIO_Config(&gpio_cfg_adc7);
     return 0;
@@ -71,7 +71,7 @@ int epic_light_sensor_get(uint16_t* value)
 {
     if (!poll_task)
     {
-        return EINVAL;
+        return -ENODATA;
     }
 	*value = last_value;
     return 0;

pycardium/modules/light_sensor.c

@@ -14,7 +14,7 @@ STATIC mp_obj_t mp_light_sensor_get_reading()
 {
     uint16_t last;
     int status = epic_light_sensor_get(&last);
-    if (status == EINVAL)
+    if (status == -ENODATA)
     {
         mp_raise_ValueError("sensor not running");
         return mp_const_none;