net: ipv6: nbr: Factor out parsing of ll address option
net: ipv6: nbr: Factor out parsing of ll address option

Use the same code when parsing source link-layer address option for
both RA and NS packets. It looked like handle_ns_neighbor() could
actually read too much data into lladdr.addr when handling 8-byte
addresses (802.15.4).

Signed-off-by: Jonas Norling <ab966cf3c8cd17a940b3653d944a1e8b292a55ac@greeneggs.se>

Vudentz/zephyr,nashif/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,nashif/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr