drm/<drivers>: Unified handling of unimplemented fb->create_handle

Some drivers don't have real ->create_handle callbacks.

- cirrus/ast/mga200: Returns either 0 or -EINVAL.

- udl: Didn't even bother with a callback, leading to a nice
  userspace-triggerable OOPS.

- vmwgfx: This driver bothered with an implementation to return 0 as
  the handle (which is the canonical no-obj gem handle).

All have in common that ->create_handle doesn't really make too much
sense for them - that ioctl is used only for seamless fb takeover in
the radeon/nouveau/i915 ddx drivers. So allow drivers to not implement
this and return a consistent -ENODEV.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c

@@ -373,16 +373,6 @@ void vmw_kms_cursor_post_execbuf(struct vmw_private *dev_priv)
  * Generic framebuffer code
  */
 
-int vmw_framebuffer_create_handle(struct drm_framebuffer *fb,
-				  struct drm_file *file_priv,
-				  unsigned int *handle)
-{
-	if (handle)
-		*handle = 0;
-
-	return 0;
-}
-
 /*
  * Surface framebuffer code
  */
@@ -610,7 +600,6 @@ int vmw_framebuffer_surface_dirty(struct drm_framebuffer *framebuffer,
 static struct drm_framebuffer_funcs vmw_framebuffer_surface_funcs = {
 	.destroy = vmw_framebuffer_surface_destroy,
 	.dirty = vmw_framebuffer_surface_dirty,
-	.create_handle = vmw_framebuffer_create_handle,
 };
 
 static int vmw_kms_new_framebuffer_surface(struct vmw_private *dev_priv,
@@ -961,7 +950,6 @@ int vmw_framebuffer_dmabuf_dirty(struct drm_framebuffer *framebuffer,
 static struct drm_framebuffer_funcs vmw_framebuffer_dmabuf_funcs = {
 	.destroy = vmw_framebuffer_dmabuf_destroy,
 	.dirty = vmw_framebuffer_dmabuf_dirty,
-	.create_handle = vmw_framebuffer_create_handle,
 };
 
 /**