drm/ast: Initialized data needed to map fbdev memory

Due to a missing initialization there was no way to map fbdev memory.
Thus for example using the Xserver with the fbdev driver failed.
This fix adds initialization for fix.smem_start and fix.smem_len
in the fb_info structure, which fixes this problem.

Requested-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: stable@vger.kernel.org
Signed-off-by: Egbert Eich <eich@suse.de>
[pulled from SuSE tree by me - airlied]
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/ast/ast_drv.h b/drivers/gpu/drm/ast/ast_drv.h
index 86205a2..05f6522 100644
--- a/drivers/gpu/drm/ast/ast_drv.h
+++ b/drivers/gpu/drm/ast/ast_drv.h
@@ -315,6 +315,7 @@
 int ast_fbdev_init(struct drm_device *dev);
 void ast_fbdev_fini(struct drm_device *dev);
 void ast_fbdev_set_suspend(struct drm_device *dev, int state);
+void ast_fbdev_set_base(struct ast_private *ast, unsigned long gpu_addr);
 
 struct ast_bo {
 	struct ttm_buffer_object bo;