media: dvb-frontends: complete kernel-doc markups

For the dvb-frontends that are now part of the documentation,
complete the kernel-doc markups, in order for them to be
properly used at the driver's kAPI documentation.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/dvb-frontends/zd1301_demod.h

@@ -52,6 +52,12 @@ struct i2c_adapter *zd1301_demod_get_i2c_adapter(struct platform_device *pdev);
 
 #else
 
+/**
+ * zd1301_demod_get_dvb_frontend() - Attach a zd1301 frontend
+ * @dev: Pointer to platform device
+ *
+ * Return: Pointer to %struct dvb_frontend or NULL if attach fails.
+ */
 static inline struct dvb_frontend *zd1301_demod_get_dvb_frontend(struct platform_device *dev)
 {
 	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);