* net/netdev/netdev_ioctl.c:
(netdev_ifr_ioctl): The ioctl SIOCSIFHWADDR sets the hardware address
(e.g., Ethernet MAC, etc.) of a network interface. Radio devices may
have different lengths of hardware addresses, such as
NET_6LOWPAN_EADDRSIZE (8), NET_6LOWPAN_SADDRSIZE (2), or
RADIO_MAX_ADDRLEN (8). Also, Kconfig CONFIG_PKTRADIO_ADDRLEN allows
the user to set any arbitrary size. Note that while the sister ioctl
SIOCGIFHWADDR "get hardware address" copies
`dev->d_mac.radio.nv_addrlen` bytes, SIOCSIFHWADDR was copying
NET_6LOWPAN_ADDRSIZE bytes unconditionally. Depending on which radio
is used, this could be incorrect. Fixing it to use
`dev->d_mac.radio.nv_addrlen` for SIOCSIFHWADDR as well. Also adding
DEBUGASSERT to ensure this is within bounds of source and
destination of the copy.