spmi: document spmi_device_from_of() refcounting

Add a comment documenting that the spmi_device_from_of() takes a
reference to the embedded struct device that needs to be dropped after
use.
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20231003152927.15000-5-johan+linaro@kernel.orgSigned-off-by: Lee Jones <lee@kernel.org>

drivers/spmi/spmi.c

@@ -392,6 +392,9 @@ static struct bus_type spmi_bus_type = {
  *
  * @np:		device node
  *
+ * Takes a reference to the embedded struct device which needs to be dropped
+ * after use.
+ *
  * Returns the struct spmi_device associated with a device node or NULL.
  */
 struct spmi_device *spmi_device_from_of(struct device_node *np)