netdevsim: remove unneeded semicolon

Eliminate the following coccicheck warning:
 drivers/net/netdevsim/fib.c:569:2-3: Unneeded semicolon

Signed-off-by: Qiheng Lin <linqiheng@huawei.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>