udlfb: fix hcd_buffer_free panic on unplug/replug

Fix race conditions with unplug/replug behavior, in particular
take care not to hold up USB probe/disconnect for long-running
framebuffer operations and rely on usb to handle teardown.

Fix for kernel panic reported with new F17 multiseat support.

Reported-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Bernie Thompson <bernie@plugable.com>
diff --git a/include/video/udlfb.h b/include/video/udlfb.h
index c41f308..f9466fa 100644
--- a/include/video/udlfb.h
+++ b/include/video/udlfb.h
@@ -41,6 +41,7 @@
 	char *backing_buffer;
 	int fb_count;
 	bool virtualized; /* true when physical usb device not present */
+	struct delayed_work init_framebuffer_work;
 	struct delayed_work free_framebuffer_work;
 	atomic_t usb_active; /* 0 = update virtual buffer, but no usb traffic */
 	atomic_t lost_pixels; /* 1 = a render op failed. Need screen refresh */