EMAC could be disabled, while there is some sb_buff
in use. That buffers got lost for linux.

In order to reproduce run on device during active ethernet work:
    ifconfig eth0 down
Signed-off-by: NAlexander Kochetkov <al.kochet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>