[media] Rename set_frontend fops to set_frontend_legacy

Passing DVBv3 parameters to set_frontend is not fun, as the
core doesn't have any way to know if the driver is using the
v3 or v5 parameters. So, rename the callback and add a new
one to allow distinguish between a mixed v3/v5 paramenter call
from a pure v5 call.

After having all frontends to use the new way, the legacy
call can be removed.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/dvb/frontends/cx24123.c b/drivers/media/dvb/frontends/cx24123.c
index 4d387d3..1342429 100644
--- a/drivers/media/dvb/frontends/cx24123.c
+++ b/drivers/media/dvb/frontends/cx24123.c
@@ -1146,7 +1146,7 @@
 	.release = cx24123_release,
 
 	.init = cx24123_initfe,
-	.set_frontend = cx24123_set_frontend,
+	.set_frontend_legacy = cx24123_set_frontend,
 	.get_frontend = cx24123_get_frontend,
 	.read_status = cx24123_read_status,
 	.read_ber = cx24123_read_ber,