at86rf230: fix is_tx while error handling

This patch fix the error handling when is_tx is true. The error handling
tries to get the transceiver into RX_AACK_ON mode then we need to be
sure that is_tx is false.
Signed-off-by: NAlexander Aring <alex.aring@gmail.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

drivers/net/ieee802154/at86rf230.c

@@ -457,6 +457,7 @@ at86rf230_async_error_recover(void *context)
 	struct at86rf230_state_change *ctx = context;
 	struct at86rf230_local *lp = ctx->lp;
 
+	lp->is_tx = 0;
 	at86rf230_async_state_change(lp, ctx, STATE_RX_AACK_ON, NULL, false);
 	ieee802154_wake_queue(lp->hw);
 }