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/Makefile

@@ -11,7 +11,8 @@ drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_agpsupport.o drm_scatter.o ati_pcigart.o drm_pci.o \
 		drm_sysfs.o drm_hashtab.o drm_sman.o drm_mm.o \
 		drm_crtc.o drm_crtc_helper.o drm_modes.o drm_edid.o \
-		drm_info.o drm_debugfs.o drm_encoder_slave.o
+		drm_info.o drm_debugfs.o drm_encoder_slave.o \
+		drm_fb_helper.o
 
 drm-$(CONFIG_COMPAT) += drm_ioc32.o