Set disconnected flag in struct usbhid when a usb device is removed. Check for
disconnected flag before sending urb requests. This prevents a kernel panic
when a hid driver calls hid_hw_request() after removing a usb device.

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000058
 IP: [<ffffffff8161746f>] hid_submit_ctrl+0x7f/0x290
 PGD 0
 Oops: 0002 [#1] PREEMPT SMP
 CPU: 2 PID: 39 Comm: khubd Tainted: G          IO  3.16.0-rc5+ #112
 Hardware name: Microsoft Corporation Surface Pro 2/Surface Pro 2, BIOS 2.03.0250 09/06/2013
 task: ffff880118aba6e0 ti: ffff8800daf80000 task.ti: ffff8800daf80000
 RIP: 0010:[<ffffffff8161746f>]  [<ffffffff8161746f>] hid_submit_ctrl+0x7f/0x290
 RSP: 0018:ffff8800daf83750  EFLAGS: 00010086
 RAX: 0000000080000300 RBX: ffff88003f60c000 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff880117f78000
 RBP: ffff8800daf83788 R08: 0000000000000001 R09: 0000000000000001
 R10: 0000000000000001 R11: 0000000000000000 R12: ffff880117f78000
 R13: ffff88003f11a290 R14: 000000000000000c R15: ffff880091cb3ab8
 FS:  0000000000000000(0000) GS:ffff88011b000000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000058 CR3: 0000000001c11000 CR4: 00000000001407e0
 Stack:
  ffff880117f3dcd0 ffff880117f78000 ffff88003f60c000 ffff880117f78000
  ffff880117f78000 ffff88003f11a290 0000000000000000 ffff8800daf837b0
  ffffffff81617707 ffff880117f78000 ffff88003f60c000 0000000000000013
 Call Trace:
  [<ffffffff81617707>] usbhid_restart_ctrl_queue+0x87/0x140
  [<ffffffff81617a88>] usbhid_submit_report+0x2c8/0x370
  [<ffffffff81617b4a>] usbhid_request+0x1a/0x30
  [<ffffffffa020edfb>] sensor_hub_set_feature+0x8b/0xd0 [hid_sensor_hub]
  [<ffffffffa02d9084>] hid_sensor_power_state+0x84/0x110 [hid_sensor_trigger]
  [<ffffffffa02d9129>] hid_sensor_data_rdy_trigger_set_state+0x19/0x20 [hid_sensor_trigger]
  [<ffffffffa034d5b7>] iio_triggered_buffer_predisable+0xa7/0xb0 [industrialio]
  [<ffffffffa034cc4a>] iio_disable_all_buffers+0x3a/0xc0 [industrialio]
  [<ffffffffa03487d3>] iio_device_unregister+0x53/0x80 [industrialio]
  [<ffffffffa026c06a>] hid_accel_3d_remove+0x2a/0x50 [hid_sensor_accel_3d]
  [<ffffffff814f433d>] platform_drv_remove+0x1d/0x40
  [<ffffffff814f18bf>] __device_release_driver+0x7f/0xf0
  [<ffffffff814f1955>] device_release_driver+0x25/0x40
  [<ffffffff814f121c>] bus_remove_device+0x11c/0x1a0
  [<ffffffff814ed7d6>] device_del+0x136/0x1e0
  [<ffffffff81512190>] ? mfd_cell_disable+0x80/0x80
  [<ffffffff814f41d1>] platform_device_del+0x21/0xc0
  [<ffffffff814f4282>] platform_device_unregister+0x12/0x30
  [<ffffffff815121d3>] mfd_remove_devices_fn+0x43/0x50
  [<ffffffff814ed3e3>] device_for_each_child+0x43/0x70
  [<ffffffff81512105>] mfd_remove_devices+0x25/0x30
  [<ffffffffa020ebd7>] sensor_hub_remove+0x87/0x140 [hid_sensor_hub]
  [<ffffffff81607c5b>] hid_device_remove+0x6b/0xd0
  [<ffffffff814f18bf>] __device_release_driver+0x7f/0xf0
  [<ffffffff814f1955>] device_release_driver+0x25/0x40
  [<ffffffff814f121c>] bus_remove_device+0x11c/0x1a0
  [<ffffffff814ed7d6>] device_del+0x136/0x1e0
  [<ffffffff81607d47>] hid_destroy_device+0x27/0x60
  [<ffffffff81616972>] usbhid_disconnect+0x22/0x50
  [<ffffffff81568597>] usb_unbind_interface+0x77/0x2b0
  [<ffffffff814f18bf>] __device_release_driver+0x7f/0xf0
  [<ffffffff814f1955>] device_release_driver+0x25/0x40
  [<ffffffff814f121c>] bus_remove_device+0x11c/0x1a0
  [<ffffffff814ed7d6>] device_del+0x136/0x1e0
  [<ffffffff81565cd1>] usb_disable_device+0x91/0x2a0
  [<ffffffff8155b046>] usb_disconnect+0x96/0x2e0
  [<ffffffff8155d74a>] hub_thread+0xb5a/0x1840
Signed-off-by: Reyad Attiyat <reyad.attiyat@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>