virtio_net: Fix code indent error

This patch fixes the checkpatch.pl warning:

ERROR: code indent should use tabs where possible #3453: FILE: drivers/net/virtio_net.c:3453: ret = register_virtio_driver(&virtio_net_driver);$

Uneccessary newline was also removed making line 3453 now 3452.

Signed-off-by: Michael Catanzaro <mcatanzaro.kernel@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>