[IPV4]: Remove unnecessary test for the loopback device from inetdev_destroy

Currently we never call unregister_netdev for the loopback device so
it is impossible for us to reach inetdev_destroy with the loopback
device.  So the test in inetdev_destroy is unnecessary.

Further when testing with my network namespace patches removing
unregistering the loopback device and calling inetdev_destroy works
fine so there appears to be no reason for avoiding unregistering the
loopback device.
Signed-off-by: NEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/devinet.c

@@ -203,8 +203,6 @@ static void inetdev_destroy(struct in_device *in_dev)
 	ASSERT_RTNL();
 
 	dev = in_dev->dev;
-	if (dev == loopback_dev)
-		return;
 
 	in_dev->dead = 1;