net: Fix coccinelle warning

kbuild test robot says:

  >coccinelle warnings: (new ones prefixed by >>)
  >>> net/core/dev.c:1588:2-3: Unneeded semicolon

So, let's remove it.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>