drm/i915: restore only the mode of this driver on lastclose (v2)

i915 calls the panic handler function on last close to reset the modes,
however this is a really bad idea for multi-gpu machines, esp shareable
gpus machines. So add a new entry point for the driver to just restore
its own fbcon mode.

v2: move code into fb helper, fix panic code to block mode change on
powered off GPUs.

[airlied: this hits drm core and I wrote it and it was reviewed on intel-gfx
 so really I signed it off twice ;-).]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 7273037..12876f2 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -2207,7 +2207,7 @@
 	drm_i915_private_t *dev_priv = dev->dev_private;
 
 	if (!dev_priv || drm_core_check_feature(dev, DRIVER_MODESET)) {
-		drm_fb_helper_restore();
+		intel_fb_restore_mode(dev);
 		vga_switcheroo_process_delayed_switch();
 		return;
 	}