net/tg3: Fix warning from pci_disable_device()

net/tg3: Fix warning from pci_disable_device()

The patch fixes following warning. The PCI device might have been
disabled somewhere else when we have EEH errors during early stage.

Device tg3 disabling already-disabled device
WARNING: at drivers/pci/pci.c:1403
:
NIP [c00000000044fd5c] .pci_disable_device+0xcc/0xe0
LR [c00000000044fd58] .pci_disable_device+0xc8/0xe0
Call Trace:
[c000003f80bc7370] [c00000000044fd58] .pci_disable_device+0xc8/0xe0
[c000003f80bc73f0] [d00000001cfe8fc0] .tg3_init_one+0x2f0/0x19f0 [tg3]
[c000003f80bc74d0] [c0000000004534e8] .local_pci_probe+0x68/0xb0
[c000003f80bc7560] [c0000000004537c8] .pci_device_probe+0x198/0x1a0
[c000003f80bc7610] [c0000000004f9e98] .driver_probe_device+0xd8/0x450
[c000003f80bc76a0] [c0000000004fa3bc] .__driver_attach+0x10c/0x110
[c000003f80bc7730] [c0000000004f6e94] .bus_for_each_dev+0x94/0x100
[c000003f80bc77d0] [c0000000004f9634] .driver_attach+0x34/0x50
[c000003f80bc7850] [c0000000004f8f98] .bus_add_driver+0x288/0x380
[c000003f80bc78f0] [c0000000004fae2c] .driver_register+0x9c/0x200
[c000003f80bc7980] [c000000000453214] .__pci_register_driver+0x64/0x90
[c000003f80bc7a10] [d00000001cff7a60] .tg3_driver_init+0x2c/0x40 [tg3]
[c000003f80bc7a80] [c00000000000b424] .do_one_initcall+0x144/0x1f0
[c000003f80bc7b70] [c0000000001244a0] .load_module+0x1f30/0x2700
[c000003f80bc7d40] [c000000000124e80] .SyS_finit_module+0xc0/0x110
[c000003f80bc7e30] [c000000000009dd4] syscall_exit+0x0/0x98

Reported-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Acked-by: Nithin Nayak Sujir <nsujir@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>