parentheses around RX_FIFO_SPACE definition

drivers/net/skfp/h/fplustm.h:129:
#define RX_FIFO_SPACE 0x4000 - RX_FIFO_OFF

drivers/net/skfp/fplustm.c:1404:

                smc->hw.fp.fifo.rx1_fifo_size = RX_FIFO_SPACE *
                SMT_R1_RXD_COUNT/(SMT_R1_RXD_COUNT+SMT_R2_RXD_COUNT) ;
                smc->hw.fp.fifo.rx2_fifo_size = RX_FIFO_SPACE *
                SMT_R2_RXD_COUNT/(SMT_R1_RXD_COUNT+SMT_R2_RXD_COUNT) ;

Add parentheses to definition to prevent operator precedence errors

---

index 98bbf65..588579c 100644
@@ -126,7 +126,7 @@ struct s_smt_rx_queue {
 #define	SYNC_TRAFFIC_ON		0x2
 
 /* big FIFO memory */
-#define	RX_FIFO_SPACE		0x4000 - RX_FIFO_OFF
+#define	RX_FIFO_SPACE		(0x4000 - RX_FIFO_OFF)
 #define	TX_FIFO_SPACE		0x4000
 
 #define	TX_SMALL_FIFO		0x0900