brcmfmac: remove set but not used variable 'old_state'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/broadcom/brcm80211/brcmfmac/usb.c: In function 'brcmf_usb_state_change':
drivers/net/wireless/broadcom/brcm80211/brcmfmac/usb.c:578:6: warning:
 variable 'old_state' set but not used [-Wunused-but-set-variable]

It's never used and can be removed.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/broadcom/brcm80211/brcmfmac/usb.c

@@ -575,7 +575,6 @@ static void
 brcmf_usb_state_change(struct brcmf_usbdev_info *devinfo, int state)
 {
 	struct brcmf_bus *bcmf_bus = devinfo->bus_pub.bus;
-	int old_state;
 
 	brcmf_dbg(USB, "Enter, current state=%d, new state=%d\n",
 		  devinfo->bus_pub.state, state);
@@ -583,7 +582,6 @@ brcmf_usb_state_change(struct brcmf_usbdev_info *devinfo, int state)
 	if (devinfo->bus_pub.state == state)
 		return;
 
-	old_state = devinfo->bus_pub.state;
 	devinfo->bus_pub.state = state;
 
 	/* update state of upper layer */