drm/kms: move driver specific fb common code to helper functions (v2)

Initially I always meant this code to be shared, but things
ran away from me before I got to it.

This refactors the i915 and radeon kms fbdev interaction layers
out into generic helpers + driver specific pieces.

It moves all the panic/sysrq enhancements to the core file,
and stores a linked list of kernel fbs. This could possibly be
improved to only store the fb which has fbcon on it for panics
etc.

radeon retains some specific codes used for a big endian
workaround.

changes:
fix oops in v1
fix freeing path for crtc_info

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/i915/i915_dma.c

@@ -29,6 +29,7 @@
 #include "drmP.h"
 #include "drm.h"
 #include "drm_crtc_helper.h"
+#include "drm_fb_helper.h"
 #include "intel_drv.h"
 #include "i915_drm.h"
 #include "i915_drv.h"
@@ -1347,7 +1348,7 @@ void i915_driver_lastclose(struct drm_device * dev)
 	drm_i915_private_t *dev_priv = dev->dev_private;
 
 	if (!dev_priv || drm_core_check_feature(dev, DRIVER_MODESET)) {
-		intelfb_restore();
+		drm_fb_helper_restore();
 		return;
 	}