mac802154: iface: fix order while interface up

This patch moves the hardware setting before calling the driver start
callback which activates the receive handling. The hardware setup
contains settings like address filtering which should be setup before
activate the receive handling on the transceiver. These setting are
protected by ieee802154_check_concurrent_iface check. This means we
need to set these registers once before calling drv_start and can't
be overwritten by other interfaces.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>