drm/i915: call drm_vblank_cleanup() earlier at unload

In its current place, it just segfaults while trying to access the
CRTC structures:

[ 9132.421681] Call Trace:
[ 9132.421707]  [<ffffffffa01130d8>] i915_get_crtc_scanoutpos+0x1e8/0x220 [i915]
[ 9132.421727]  [<ffffffffa001da34>] drm_calc_vbltimestamp_from_scanoutpos+0x94/0x330 [drm]
[ 9132.421744]  [<ffffffffa001d240>] ?vblank_disable_and_save+0x40/0x1e0 [drm]
[ 9132.421769]  [<ffffffffa0114328>] i915_get_vblank_timestamp+0x68/0xb0 [i915]
[ 9132.421786]  [<ffffffffa001d094>] drm_get_last_vbltimestamp+0x44/0x80 [drm]
[ 9132.421801]  [<ffffffffa001d3a6>] vblank_disable_and_save+0x1a6/0x1e0 [drm]
[ 9132.421817]  [<ffffffffa001eac1>] drm_vblank_cleanup+0x61/0xa0 [drm]
[ 9132.421849]  [<ffffffffa0177a5e>] i915_driver_unload+0xde/0x290 [i915]
[ 9132.421867]  [<ffffffffa0020264>] drm_dev_unregister+0x24/0xb0 [drm]
[ 9132.421884]  [<ffffffffa002090e>] drm_put_dev+0x1e/0x70 [drm]
[ 9132.421901]  [<ffffffffa00e01e0>] i915_pci_remove+0x10/0x20 [i915]
[ 9132.421910]  [<ffffffff81347556>] pci_device_remove+0x36/0xb0
[ 9132.421920]  [<ffffffff8140084a>] __device_release_driver+0x7a/0xf0
[ 9132.421928]  [<ffffffff81400fc8>] driver_detach+0xb8/0xc0
[ 9132.421936]  [<ffffffff8140054a>] bus_remove_driver+0x4a/0xb0
[ 9132.421944]  [<ffffffff81401717>] driver_unregister+0x27/0x50
[ 9132.421953]  [<ffffffff81346f65>] pci_unregister_driver+0x25/0x70
[ 9132.421971]  [<ffffffffa00229c8>] drm_pci_exit+0x78/0xa0 [drm]
[ 9132.422000]  [<ffffffffa017a6d2>] i915_exit+0x20/0x94e [i915]
[ 9132.422009]  [<ffffffff810fb9dc>] SyS_delete_module+0x13c/0x1f0
[ 9132.422019]  [<ffffffff8131c5fb>] ?
trace_hardirqs_on_thunk+0x3a/0x3f
[ 9132.422028]  [<ffffffff816f7792>] system_call_fastpath+0x16/0x1b

This means it has to be before intel_modeset_cleanup, which cleans the
CRTC structures. But if we move it to before intel_fbdev_fini(), we
get WARNs because intel_fbdev_fini() still tries to use the vblanks,
so the only acceptable point for drm_vblank_cleanup() seems to be this
place.

Related commit:

    commit cbb47d179fb345c579cd8cd884693903fceed26a
    Author: Chris Wilson <chris@chris-wilson.co.uk>
    Date:   Mon Sep 23 17:33:20 2013 -0300
        drm/i915: Add some missing steps to i915_driver_load error path

Testsuite: igt/drv_module_reload
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77511
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83484
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1853,8 +1853,12 @@ int i915_driver_unload(struct drm_device *dev)
 
 	acpi_video_unregister();
 
-	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+	if (drm_core_check_feature(dev, DRIVER_MODESET))
 		intel_fbdev_fini(dev);
+
+	drm_vblank_cleanup(dev);
+
+	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
 		intel_modeset_cleanup(dev);
 
 		/*
@@ -1895,8 +1899,6 @@ int i915_driver_unload(struct drm_device *dev)
 			i915_free_hws(dev);
 	}
 
-	drm_vblank_cleanup(dev);
-
 	intel_teardown_gmbus(dev);
 	intel_teardown_mchbar(dev);