e1000: fix disabling already-disabled warning

e1000: fix disabling already-disabled warning

This patch adds check so that driver does not disable already
disabled device.

[   44.637743] advantechwdt: Unexpected close, not stopping watchdog!
[   44.997548] input: ImExPS/2 Generic Explorer Mouse as /devices/platform/i8042/serio1/input/input6
[   45.013419] e1000 0000:00:03.0: disabling already-disabled device
[   45.013447] ------------[ cut here ]------------
[   45.014868] WARNING: CPU: 1 PID: 71 at drivers/pci/pci.c:1641 pci_disable_device+0xa1/0x105:
						pci_disable_device at drivers/pci/pci.c:1640
[   45.016171] CPU: 1 PID: 71 Comm: rcu_perf_shutdo Not tainted 4.14.0-01330-g3c07399 #1
[   45.017197] task: ffff88011bee9e40 task.stack: ffffc90000860000
[   45.017987] RIP: 0010:pci_disable_device+0xa1/0x105:
						pci_disable_device at drivers/pci/pci.c:1640
[   45.018603] RSP: 0000:ffffc90000863e30 EFLAGS: 00010286
[   45.019282] RAX: 0000000000000035 RBX: ffff88013a230008 RCX: 0000000000000000
[   45.020182] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000203
[   45.021084] RBP: ffff88013a3f31e8 R08: 0000000000000001 R09: 0000000000000000
[   45.021986] R10: ffffffff827ec29c R11: 0000000000000002 R12: 0000000000000001
[   45.022946] R13: ffff88013a230008 R14: ffff880117802b20 R15: ffffc90000863e8f
[   45.023842] FS:  0000000000000000(0000) GS:ffff88013fd00000(0000) knlGS:0000000000000000
[   45.024863] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   45.025583] CR2: ffffc900006d4000 CR3: 000000000220f000 CR4: 00000000000006a0
[   45.026478] Call Trace:
[   45.026811]  __e1000_shutdown+0x1d4/0x1e2:
						__e1000_shutdown at drivers/net/ethernet/intel/e1000/e1000_main.c:5162
[   45.027344]  ? rcu_perf_cleanup+0x2a1/0x2a1:
						rcu_perf_shutdown at kernel/rcu/rcuperf.c:627
[   45.027883]  e1000_shutdown+0x14/0x3a:
						e1000_shutdown at drivers/net/ethernet/intel/e1000/e1000_main.c:5235
[   45.028351]  device_shutdown+0x110/0x1aa:
						device_shutdown at drivers/base/core.c:2807
[   45.028858]  kernel_power_off+0x31/0x64:
						kernel_power_off at kernel/reboot.c:260
[   45.029343]  rcu_perf_shutdown+0x9b/0xa7:
						rcu_perf_shutdown at kernel/rcu/rcuperf.c:637
[   45.029852]  ? __wake_up_common_lock+0xa2/0xa2:
						autoremove_wake_function at kernel/sched/wait.c:376
[   45.030414]  kthread+0x126/0x12e:
						kthread at kernel/kthread.c:233
[   45.030834]  ? __kthread_bind_mask+0x8e/0x8e:
						kthread at kernel/kthread.c:190
[   45.031399]  ? ret_from_fork+0x1f/0x30:
						ret_from_fork at arch/x86/entry/entry_64.S:443
[   45.031883]  ? kernel_init+0xa/0xf5:
						kernel_init at init/main.c:997
[   45.032325]  ret_from_fork+0x1f/0x30:
						ret_from_fork at arch/x86/entry/entry_64.S:443
[   45.032777] Code: 00 48 85 ed 75 07 48 8b ab a8 00 00 00 48 8d bb 98 00 00 00 e8 aa d1 11 00 48 89 ea 48 89 c6 48 c7 c7 d8 e4 0b 82 e8 55 7d da ff <0f> ff b9 01 00 00 00 31 d2 be 01 00 00 00 48 c7 c7 f0 b1 61 82
[   45.035222] ---[ end trace c257137b1b1976ef ]---
[   45.037838] ACPI: Preparing to enter system sleep state S5

Signed-off-by: Tushar Dave <tushar.n.dave@oracle.com>
Tested-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>