[media] stv090x: Some whitespace cleanups

While writing changeset fdf1bc9fa2, I noticed some checkpatch
complains about the CodingStyle for function parameters. So,
clean them.

While here, also removes uneeded "extern" from function prototype.

No functional changes.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/dvb-frontends/stv090x.h

@@ -109,7 +109,7 @@ struct stv090x_config {
 
 #if IS_ENABLED(CONFIG_DVB_STV090x)
 
-extern struct dvb_frontend *stv090x_attach(struct stv090x_config *config,
+struct dvb_frontend *stv090x_attach(struct stv090x_config *config,
 				    struct i2c_adapter *i2c,
 				    enum stv090x_demodulator demod);