[media] drxd_hard: fix sparse warnings

drivers/media/dvb-frontends/drxd_hard.c:1017:70: warning: Using plain integer as NULL pointer
drivers/media/dvb-frontends/drxd_hard.c:1038:69: warning: Using plain integer as NULL pointer
drivers/media/dvb-frontends/drxd_hard.c:2836:33: warning: Using plain integer as NULL pointer
drivers/media/dvb-frontends/drxd_hard.c:2972:30: warning: Using plain integer as NULL pointer

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Reviewed-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/dvb-frontends/drxd_hard.c

@@ -1014,7 +1014,7 @@ static int HI_CfgCommand(struct drxd_state *state)
 		status = Write16(state, HI_RA_RAM_SRV_CMD__A,
 				 HI_RA_RAM_SRV_CMD_CONFIG, 0);
 	else
-		status = HI_Command(state, HI_RA_RAM_SRV_CMD_CONFIG, 0);
+		status = HI_Command(state, HI_RA_RAM_SRV_CMD_CONFIG, NULL);
 	mutex_unlock(&state->mutex);
 	return status;
 }
@@ -1035,7 +1035,7 @@ static int HI_ResetCommand(struct drxd_state *state)
 	status = Write16(state, HI_RA_RAM_SRV_RST_KEY__A,
 			 HI_RA_RAM_SRV_RST_KEY_ACT, 0);
 	if (status == 0)
-		status = HI_Command(state, HI_RA_RAM_SRV_CMD_RESET, 0);
+		status = HI_Command(state, HI_RA_RAM_SRV_CMD_RESET, NULL);
 	mutex_unlock(&state->mutex);
 	msleep(1);
 	return status;
@@ -2833,7 +2833,7 @@ static int drxd_init(struct dvb_frontend *fe)
 	int err = 0;
 
 /*	if (request_firmware(&state->fw, "drxd.fw", state->dev)<0) */
-	return DRXD_init(state, 0, 0);
+	return DRXD_init(state, NULL, 0);
 
 	err = DRXD_init(state, state->fw->data, state->fw->size);
 	release_firmware(state->fw);
@@ -2969,7 +2969,7 @@ struct dvb_frontend *drxd_attach(const struct drxd_config *config,
 
 	mutex_init(&state->mutex);
 
-	if (Read16(state, 0, 0, 0) < 0)
+	if (Read16(state, 0, NULL, 0) < 0)
 		goto error;
 
 	state->frontend.ops = drxd_ops;