i915: remove pm_qos request on error

Not removing pm qos request and free memory for it can cause crash,
when some other driver use pm qos. For example, this oops:

BUG: unable to handle kernel paging request at fffffffffffffff8
IP: [<ffffffff81307a6b>] plist_add+0x5b/0xd0
Call Trace:
 [<ffffffff810acf25>] pm_qos_update_target+0x125/0x1e0
 [<ffffffff810ad071>] pm_qos_add_request+0x91/0x100
 [<ffffffffa053ec14>] e1000_open+0xe4/0x5b0 [e1000e]

was caused by earlier i915 probe failure:

[drm:i915_report_and_clear_eir] *ERROR* EIR stuck: 0x00000010, masking
[drm:init_ring_common] *ERROR* render ring initialization failed ctl 0001f001 head 00003004 tail 00000000 start 00003000
[drm:i915_driver_load] *ERROR* failed to init modeset
i915: probe of 0000:00:02.0 failed with error -5

Bug report:
http://bugzilla.redhat.com/show_bug.cgi?id=1057533

Reported-by: Giandomenico De Tullio <ghisha@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
[danvet: Drop unnecessary code movement.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1685,6 +1685,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 
 	intel_teardown_gmbus(dev);
 	intel_teardown_mchbar(dev);
+	pm_qos_remove_request(&dev_priv->pm_qos);
 	destroy_workqueue(dev_priv->wq);
 out_mtrrfree:
 	arch_phys_wc_del(dev_priv->gtt.mtrr);