[media] rtl2832: disable regmap register cache

Caching register reads causes some random I/O errors on channel
change. Disable caching now in order to avoid those errors.

Reverts partly commit dcadb82aSigned-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/dvb-frontends/rtl2832.c

@@ -1240,7 +1240,7 @@ static int rtl2832_probe(struct i2c_client *client,
 	dev->regmap_config.max_register = 5 * 0x100,
 	dev->regmap_config.ranges = regmap_range_cfg,
 	dev->regmap_config.num_ranges = ARRAY_SIZE(regmap_range_cfg),
-	dev->regmap_config.cache_type = REGCACHE_RBTREE,
+	dev->regmap_config.cache_type = REGCACHE_NONE,
 	dev->regmap = regmap_init(&client->dev, &regmap_bus, client,
 				  &dev->regmap_config);
 	if (IS_ERR(dev->regmap)) {