mei: nfc: fix nfc device freeing

The nfc_dev is a static variable and is not cleaned properly upon reset
mainly ndev->cl and ndev->cl_info are not set to NULL after freeing which

mei_stop:198: mei_me 0000:00:16.0: stopping the device.
[  404.253427] general protection fault: 0000 [#2] SMP
[  404.253437] Modules linked in: mei_me(-) binfmt_misc snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device edd af_packet cpufreq_conservative cpufreq_userspace cpufreq_powersave fuse loop dm_mod hid_generic usbhid hid coretemp acpi_cpufreq mperf kvm_intel kvm crc32c_intel ghash_clmulni_intel aesni_intel ablk_helper cryptd lrw gf128mul snd_hda_codec_hdmi glue_helper aes_x86_64 e1000e snd_hda_intel snd_hda_codec ehci_pci iTCO_wdt iTCO_vendor_support ehci_hcd snd_hwdep xhci_hcd snd_pcm usbcore ptp mei sg microcode snd_timer pps_core i2c_i801 snd pcspkr battery rtc_cmos lpc_ich mfd_core soundcore usb_common snd_page_alloc ac ext3 jbd mbcache drm_kms_helper drm intel_agp i2c_algo_bit intel_gtt i2c_core sd_mod crc_t10dif thermal fan video button processor thermal_sys hwmon ahci libahci libata scsi_mod [last unloaded: mei_me]
[  404.253591] CPU: 0 PID: 5551 Comm: modprobe Tainted: G      D W    3.10.0-rc3 #1
[  404.253611] task: ffff880143cd8300 ti: ffff880144a2a000 task.ti: ffff880144a2a000
[  404.253619] RIP: 0010:[<ffffffff81334e5d>]  [<ffffffff81334e5d>] device_del+0x1d/0x1d0
[  404.253638] RSP: 0018:ffff880144a2bcf8  EFLAGS: 00010206
[  404.253645] RAX: 2020302e30202030 RBX: ffff880144fdb000 RCX: 0000000000000086
[  404.253652] RDX: 0000000000000001 RSI: 0000000000000086 RDI: ffff880144fdb000
[  404.253659] RBP: ffff880144a2bd18 R08: 0000000000000651 R09: 0000000000000006
[  404.253666] R10: 0000000000000651 R11: 0000000000000006 R12: ffff880144fdb000
[  404.253673] R13: ffff880149371098 R14: ffff880144482c00 R15: ffffffffa04710e0
[  404.253681] FS:  00007f251c59a700(0000) GS:ffff88014e200000(0000) knlGS:0000000000000000
[  404.253689] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  404.253696] CR2: ffffffffff600400 CR3: 0000000145319000 CR4: 00000000001407f0
[  404.253703] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  404.253710] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  404.253716] Stack:
[  404.253720]  ffff880144fdb000 ffff880143ffe000 ffff880149371098 ffffffffa0471000
[  404.253732]  ffff880144a2bd38 ffffffff8133502d ffff88014e20cf48 ffff880143ffe1d8
[  404.253744]  ffff880144a2bd48 ffffffffa02a4749 ffff880144a2bd58 ffffffffa02a4ba1
[  404.253755] Call Trace:
[  404.253766]  [<ffffffff8133502d>] device_unregister+0x1d/0x60
[  404.253787]  [<ffffffffa02a4749>] mei_cl_remove_device+0x9/0x10 [mei]
[  404.253804]  [<ffffffffa02a4ba1>] mei_nfc_host_exit+0x21/0x30 [mei]
[  404.253819]  [<ffffffffa029c2dd>] mei_stop+0x3d/0x90 [mei]
[  404.253830]  [<ffffffffa046e220>] mei_me_remove+0x60/0xe0 [mei_me]
[  404.253843]  [<ffffffff81278f37>] pci_device_remove+0x37/0xb0
[  404.253855]  [<ffffffff81337c68>] __device_release_driver+0x98/0x100
[  404.253865]  [<ffffffff81337d80>] driver_detach+0xb0/0xc0
[  404.253876]  [<ffffffff81336b4f>] bus_remove_driver+0x8f/0x120
[  404.253891]  [<ffffffff81075990>] ? try_to_wake_up+0x2b0/0x2b0
[  404.253903]  [<ffffffff81338a48>] driver_unregister+0x58/0x90
[  404.253913]  [<ffffffff8127906b>] pci_unregister_driver+0x2b/0xb0
[  404.253924]  [<ffffffffa046f244>] mei_me_driver_exit+0x10/0xdcc [mei_me]
[  404.253936]  [<ffffffff810a50d8>] SyS_delete_module+0x198/0x2b0
[  404.253949]  [<ffffffff814850d9>] ? do_page_fault+0x9/0x10
[  404.253961]  [<ffffffff81489692>] system_call_fastpath+0x16/0x1b
[  404.253967] Code: 41 5c 41 5d 41 5e 41 5f c9 c3 0f 1f 40 00 55 48 89 e5 41 56 41 55 41 54 49 89 fc 53 48 8b 87 88 00 00 00 4c 8b 37 48 85 c0 74 18 <48> 8b 78 78 4c 89 e2 be 02 00 00 00 48 81 c7 f8 00 00 00 e8 3b
[  404.254048] RIP  [<ffffffff81334e5d>] device_del+0x1d/0x1d0

Cc: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/nfc.c

@@ -142,6 +142,8 @@ static void mei_nfc_free(struct mei_nfc_dev *ndev)
 		mei_cl_unlink(ndev->cl_info);
 		kfree(ndev->cl_info);
 	}
+
+	memset(ndev, 0, sizeof(struct mei_nfc_dev));
 }
 
 static int mei_nfc_build_bus_name(struct mei_nfc_dev *ndev)