mei: drop the warning when cl is not initialized during unlinking

On systems where wd and amthif is not initialized
we will hit cl->dev == NULL. This condition is okay
so we don't need to be laud about it.

Fixes the follwing warning during suspend
[  137.061985] WARNING: at drivers/misc/mei/client.c:315 mei_cl_unlink+0x86/0x90 [mei]()
[  137.061986] Hardware name: 530U3BI/530U4BI/530U4BH
[  137.062140] Modules linked in: snd_hda_codec_hdmi snd_hda_codec_realtek joydev coretemp kvm_intel snd_hda_intel snd_hda_codec kvm arc4 iwldvm snd_hwdep i915 snd_pcm mac80211 ghash_clmulni_intel snd_page_alloc aesni_intel snd_seq_midi xts snd_seq_midi_event aes_x86_64 rfcomm snd_rawmidi parport_pc bnep lrw snd_seq uvcvideo i2c_algo_bit ppdev gf128mul iwlwifi snd_timer drm_kms_helper ablk_helper cryptd drm snd_seq_device videobuf2_vmalloc psmouse videobuf2_memops snd cfg80211 btusb videobuf2_core soundcore videodev lp bluetooth samsung_laptop wmi microcode mei serio_raw mac_hid video hid_generic lpc_ich parport usbhid hid r8169
[  137.062143] Pid: 2706, comm: kworker/u:15 Tainted: G      D W    3.8.0-rc2-next20130109-1-iniza-generic #1
[  137.062144] Call Trace:
[  137.062156]  [<ffffffff8105860f>] warn_slowpath_common+0x7f/0xc0
[  137.062159]  [<ffffffff8135b1ea>] ? ioread32+0x3a/0x40
[  137.062162]  [<ffffffff8105866a>] warn_slowpath_null+0x1a/0x20
[  137.062168]  [<ffffffffa0076be6>] mei_cl_unlink+0x86/0x90 [mei]
[  137.062173]  [<ffffffffa0071325>] mei_reset+0xc5/0x240 [mei]
[  137.062178]  [<ffffffffa0073703>] mei_pci_resume+0xa3/0x110 [mei]
[  137.062183]  [<ffffffff81379cae>] pci_pm_resume+0x7e/0xe0
[  137.062185]  [<ffffffff81379c30>] ? pci_pm_thaw+0x80/0x80
[  137.062189]  [<ffffffff8145a415>] dpm_run_callback.isra.6+0x25/0x50
[  137.062192]  [<ffffffff8145a6cf>] device_resume+0x9f/0x140
[  137.062194]  [<ffffffff8145a791>] async_resume+0x21/0x50
[  137.062200]  [<ffffffff810858b0>] async_run_entry_fn+0x90/0x1c0
[  137.062203]  [<ffffffff810778e5>] process_one_work+0x155/0x460
[  137.062207]  [<ffffffff81078578>] worker_thread+0x168/0x400
[  137.062210]  [<ffffffff81078410>] ? manage_workers+0x2b0/0x2b0
[  137.062214]  [<ffffffff8107d9f0>] kthread+0xc0/0xd0
[  137.062218]  [<ffffffff8107d930>] ? flush_kthread_worker+0xb0/0xb0
[  137.062222]  [<ffffffff816bac6c>] ret_from_fork+0x7c/0xb0
[  137.062228]  [<ffffffff8107d930>] ? flush_kthread_worker+0xb0/0xb0

Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/client.c

@@ -312,8 +312,9 @@ int mei_cl_unlink(struct mei_cl *cl)
 	if (!cl)
 		return 0;
 
-	if (WARN_ON(!cl->dev))
-		return -EINVAL;
+	/* wd and amthif might not be initialized */
+	if (!cl->dev)
+		return 0;
 
 	dev = cl->dev;