btrfs: remove duplicate included header from fs.h

Remove duplicate included header file linux/blkdev.h .
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/fs.h

@@ -9,7 +9,6 @@
 #include <linux/compiler.h>
 #include <linux/math.h>
 #include <linux/atomic.h>
-#include <linux/blkdev.h>
 #include <linux/percpu_counter.h>
 #include <linux/completion.h>
 #include <linux/lockdep.h>