tests: net: ipv6: Verify Route Info data in Router Advertisment
tests: net: ipv6: Verify Route Info data in Router Advertisment

Verify that Route Info data received in Router Advertisment creates a
route and correctly populates the net_route_entry structure.

Additionally, extend the MTU on the test interface, to accomodate the
extended Router Advertisement message.

Signed-off-by: Robert Lubos <9d28997c6894a2d0321a7bb399169af7ce99b64e@nordicsemi.no>

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