net: smc91x: Fix possible memory leak in smc_drv_probe()

If try_toggle_control_gpio() failed in smc_drv_probe(), free_netdev(ndev)
should be called to free the ndev created earlier. Otherwise, a memleak
will occur.

Fixes: 7d2911c4 ("net: smc91x: Fix gpios for device tree based booting")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>