libertas_tf: Remove duplicate struct declaration

struct lbtf_private is declared twice. One has been declared
at 157th line. Remove the duplicate.
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210331023557.2804128-4-wanjiabing@vivo.com

drivers/net/wireless/marvell/libertas_tf/libertas_tf.h

@@ -453,7 +453,6 @@ struct cmd_ds_802_11_beacon_set {
 	u8 beacon[MRVL_MAX_BCN_SIZE];
 };
 
-struct lbtf_private;
 struct cmd_ctrl_node;
 
 /** Function Prototype Declaration */