Revert "[media] dvb_frontend: return -ENOTTY for unimplement IOCTL"

As reported by Klaus Schmidinger:
"In VDR I use an ioctl() call with FE_READ_UNCORRECTED_BLOCKS on a
device (using stb0899). After this call I check 'errno' for
EOPNOTSUPP to determine whether this device supports this call. This
used to work just fine, until a few months ago I noticed that my
devices using stb0899 didn't display their signal quality in VDR's OSD
any more. After further investigation I found that
ioctl(FE_READ_UNCORRECTED_BLOCKS) no longer returns EOPNOTSUPP, but
rather ENOTTY. And since I stop getting the signal quality in case
any unknown errno value appears, this broke my signal quality query
function."

While the changes reflect what is there at:

http://comments.gmane.org/gmane.linux.kernel/1235728

it does cause regression on userspace. So, revert it to stop the
damage.

This reverts commit 177ffe506cf8 ("[media] dvb_frontend: return -ENOTTY
for unimplement IOCTL").

Reported-by: Klaus Schmidinger <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/media/dvb-core/dvb_frontend.c

···
 	struct dvb_frontend *fe = dvbdev->priv;
 	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
 	struct dvb_frontend_private *fepriv = fe->frontend_priv;
-	int err = -ENOTTY;
+	int err = -EOPNOTSUPP;
 
 	dev_dbg(fe->dvb->device, "%s: (%d)\n", __func__, _IOC_NR(cmd));
 	if (fepriv->exit != DVB_FE_NO_EXIT)
···
 		}
 
 	} else
-		err = -ENOTTY;
+		err = -EOPNOTSUPP;
 
 out:
 	kfree(tvp);
···
 	struct dvb_frontend *fe = dvbdev->priv;
 	struct dvb_frontend_private *fepriv = fe->frontend_priv;
 	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
-	int err = -ENOTTY;
+	int err = -EOPNOTSUPP;
 
 	switch (cmd) {
 	case FE_GET_INFO: {