b43: correct warning for uninitialized variable 'macstat'

  CC [M]  drivers/net/wireless/b43/pio.o
drivers/net/wireless/b43/pio.c: In function ‘pio_rx_frame’:
drivers/net/wireless/b43/pio.c:614:6: warning: ‘macstat’ may be used uninitialized in this function
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/b43/pio.c

@@ -611,7 +611,7 @@ static bool pio_rx_frame(struct b43_pio_rxqueue *q)
 	struct b43_wldev *dev = q->dev;
 	struct b43_wl *wl = dev->wl;
 	u16 len;
-	u32 macstat;
+	u32 macstat = 0;
 	unsigned int i, padding;
 	struct sk_buff *skb;
 	const char *err_msg = NULL;