[media] rtl28xxu: remove unused SDR attach logic

That logic was duplicated from rtl2832_sdr.h in order to avoid hard
dependency for staging directory. rtl2832_sdr is moved to media, so
we could remove that code now.
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/usb/dvb-usb-v2/rtl28xxu.c

@@ -24,6 +24,7 @@
 
 #include "rtl2830.h"
 #include "rtl2832.h"
+#include "rtl2832_sdr.h"
 #include "mn88472.h"
 #include "mn88473.h"
 
@@ -37,25 +38,6 @@
 #include "tua9001.h"
 #include "r820t.h"
 
-/*
- * RTL2832_SDR module is in staging. That logic is added in order to avoid any
- * hard dependency to drivers/staging/ directory as we want compile mainline
- * driver even whole staging directory is missing.
- */
-#include <media/v4l2-subdev.h>
-
-#if IS_ENABLED(CONFIG_DVB_RTL2832_SDR)
-struct dvb_frontend *rtl2832_sdr_attach(struct dvb_frontend *fe,
-	struct i2c_adapter *i2c, const struct rtl2832_config *cfg,
-	struct v4l2_subdev *sd);
-#else
-static inline struct dvb_frontend *rtl2832_sdr_attach(struct dvb_frontend *fe,
-	struct i2c_adapter *i2c, const struct rtl2832_config *cfg,
-	struct v4l2_subdev *sd)
-{
-	return NULL;
-}
-#endif
 
 #ifdef CONFIG_MEDIA_ATTACH
 #define dvb_attach_sdr(FUNCTION, ARGS...) ({ \