net: Enable IPv6 neighbor discovery by default
net: Enable IPv6 neighbor discovery by default

The IPv6 neighbor discovery is needed when dealing with real
brearers like 802.15.4, so enabling ND by default.
In Qemu and if SLIP is used, then the ND needs to be disabled
as it does not work properly with tun devices.

Change-Id: I8baf11e71fb546b698a0a3d18fcacb142744db60
Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

mirzak/zephyr-os,ldts/zephyr,zephyriot/zephyr,GiulianoFranchetto/zephyr,mirzak/zephyr-os,punitvara/zephyr,sharronliu/zephyr,32bitmicro/zephyr,finikorg/zephyr,zephyriot/zephyr,fractalclone/zephyr-riscv,fbsder/zephyr,Vudentz/zephyr,punitvara/zephyr,bigdinotech/zephyr,explora26/zephyr,rsalveti/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,sharronliu/zephyr,galak/zephyr,galak/zephyr,fbsder/zephyr,explora26/zephyr,Vudentz/zephyr,aceofall/zephyr-iotos,aceofall/zephyr-iotos,erwango/zephyr,nashif/zephyr,pklazy/zephyr,nashif/zephyr,galak/zephyr,32bitmicro/zephyr,finikorg/zephyr,mirzak/zephyr-os,sharronliu/zephyr,punitvara/zephyr,fbsder/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,erwango/zephyr,aceofall/zephyr-iotos,rsalveti/zephyr,finikorg/zephyr,explora26/zephyr,jamesonwilliams/zephyr-kernel,explora26/zephyr,punitvara/zephyr,coldnew/zephyr-project-fork,pklazy/zephyr,ldts/zephyr,runchip/zephyr-cc3220,jamesonwilliams/zephyr-kernel,32bitmicro/zephyr,fractalclone/zephyr-riscv,fbsder/zephyr,nashif/zephyr,Vudentz/zephyr,runchip/zephyr-cc3220,fractalclone/zephyr-riscv,pklazy/zephyr,holtmann/zephyr,galak/zephyr,rsalveti/zephyr,kraj/zephyr,bboozzoo/zephyr,erwango/zephyr,zephyriot/zephyr,tidyjiang8/zephyr-doc,erwango/zephyr,tidyjiang8/zephyr-doc,kraj/zephyr,fbsder/zephyr,mirzak/zephyr-os,finikorg/zephyr,tidyjiang8/zephyr-doc,coldnew/zephyr-project-fork,zephyrproject-rtos/zephyr,runchip/zephyr-cc3220,zephyrproject-rtos/zephyr,bboozzoo/zephyr,mbolivar/zephyr,runchip/zephyr-cc3200,finikorg/zephyr,fractalclone/zephyr-riscv,runchip/zephyr-cc3200,mbolivar/zephyr,Vudentz/zephyr,bigdinotech/zephyr,mbolivar/zephyr,nashif/zephyr,explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,mirzak/zephyr-os,aceofall/zephyr-iotos,32bitmicro/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,runchip/zephyr-cc3200,jamesonwilliams/zephyr-kernel,holtmann/zephyr,galak/zephyr,bboozzoo/zephyr,erwango/zephyr,pklazy/zephyr,tidyjiang8/zephyr-doc,pklazy/zephyr,holtmann/zephyr,holtmann/zephyr,kraj/zephyr,ldts/zephyr,tidyjiang8/zephyr-doc,nashif/zephyr,punitvara/zephyr,mbolivar/zephyr,fractalclone/zephyr-riscv,kraj/zephyr,mbolivar/zephyr,bigdinotech/zephyr,bigdinotech/zephyr,zephyrproject-rtos/zephyr,runchip/zephyr-cc3200,kraj/zephyr,holtmann/zephyr,runchip/zephyr-cc3220,ldts/zephyr,jamesonwilliams/zephyr-kernel,bboozzoo/zephyr,rsalveti/zephyr,coldnew/zephyr-project-fork,rsalveti/zephyr,bigdinotech/zephyr,aceofall/zephyr-iotos,sharronliu/zephyr,sharronliu/zephyr,32bitmicro/zephyr,jamesonwilliams/zephyr-kernel,ldts/zephyr,coldnew/zephyr-project-fork,coldnew/zephyr-project-fork,zephyriot/zephyr,runchip/zephyr-cc3220,bboozzoo/zephyr,runchip/zephyr-cc3200