fakelb: allow to run as monitor

For my RIOT-OS in userspace experiments I need to create a fakelb
monitor interface. The fakelb doesn't filter anything on L2 and is a
purely raw interface. Because nl802154 checks on promiscuous mode which
need to supported by creating monitors this patch adds some no-op
promiscuous mode setting and the promiscuous flag.

Signed-off-by: Alexander Aring <[e-mail]>
Signed-off-by: Marcel Holtmann <[e-mail]>

drivers/net/ieee802154/fakelb.c

···
 	write_unlock_bh(&fakelb_ifup_phys_lock);
 }
 
+static int
+fakelb_set_promiscuous_mode(struct ieee802154_hw *hw, const bool on)
+{
+	return 0;
+}
+
 static const struct ieee802154_ops fakelb_ops = {
 	.owner = THIS_MODULE,
 	.xmit_async = fakelb_hw_xmit,
···
 	.set_channel = fakelb_hw_channel,
 	.start = fakelb_hw_start,
 	.stop = fakelb_hw_stop,
+	.set_promiscuous_mode = fakelb_set_promiscuous_mode,
 };
 
 /* Number of dummy devices to be set up by this module. */
···
 	hw->phy->current_channel = 13;
 	phy->channel = hw->phy->current_channel;
 
+	hw->flags = IEEE802154_HW_PROMISCUOUS;
 	hw->parent = dev;
 
 	err = ieee802154_register_hw(hw);