8139too: Fix the lack of pci_disable_device

For linux-3.18.0
When pci_request_regions is failed in rtl8139_init_board, pci_disable_device
is not called to disable the device which are enabled by pci_enable_device,
because of disable_dev_on_err is not assigned 1.
This patch fix this problem.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>