[media] cx24120: make sure tuner is locked at get_frontend

Change get_frontend to re-check current lock status rather than relying
on a cached value from get_status. Removes potential for tuning failure
if get_frontend is called during tuning.

Probably not too essential as other changes work around this:
https://patchwork.linuxtv.org/patch/32845/Signed-off-by: Jemma Denson <jdenson@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/dvb-frontends/cx24120.c

@@ -1507,11 +1507,13 @@ static int cx24120_get_frontend(struct dvb_frontend *fe,
 {
 	struct cx24120_state *state = fe->demodulator_priv;
 	u8 freq1, freq2, freq3;
+	int status;
 
 	dev_dbg(&state->i2c->dev, "\n");
 
 	/* don't return empty data if we're not tuned in */
-	if ((state->fe_status & FE_HAS_LOCK) == 0)
+	status = cx24120_readreg(state, CX24120_REG_STATUS);
+	if (!(status & CX24120_HAS_LOCK))
 		return 0;
 
 	/* Get frequency */