rtw89: ser: fix unannotated fall-through

add `break` to fix warning of unannotated fall-through between switch
labels.

Fixes: 14f9f479 ("rtw89: ser: control hci interrupts on/off by state")
Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220408001353.17188-2-pkshih@realtek.com

drivers/net/wireless/realtek/rtw89/ser.c

@@ -394,6 +394,7 @@ static void ser_idle_st_hdl(struct rtw89_ser *ser, u8 evt)
 		break;
 	case SER_EV_STATE_OUT:
 		rtw89_hci_recovery_start(rtwdev);
+		break;
 	default:
 		break;
 	}