vdpa_sim_blk: remove duplicate include of linux/blkdev.h

In commit 7d189f61 ("vdpa_sim_blk: implement ramdisk behaviour")
linux/blkdev.h was included here causing the duplicate include.
Remove the later duplicate include.
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Link: https://lore.kernel.org/r/20210510024307.7143-1-wanjiabing@vivo.comReviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa_sim/vdpa_sim_blk.c

@@ -15,7 +15,6 @@
 #include <linux/blkdev.h>
 #include <linux/vringh.h>
 #include <linux/vdpa.h>
-#include <linux/blkdev.h>
 #include <uapi/linux/virtio_blk.h>
 
 #include "vdpa_sim.h"