net: shell: Fix the output of route command
net: shell: Fix the output of route command

Print route information by groupping them for each network
interface like this:

IPv6 routes for interface 0xa8007140
====================================
IPv6 prefix : 2001:db8::212:4b00:0:3/128
        neighbor  : 0xa80065e0
        link addr : 00:12:4B:00:00:00:00:03
IPv6 prefix : 2001:db8::212:4b00:0:1/128
        neighbor  : 0xa8006660
        link addr : 00:12:4B:00:00:00:00:01

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

fbsder/zephyr,rsalveti/zephyr,explora26/zephyr,rsalveti/zephyr,rsalveti/zephyr,runchip/zephyr-cc3220,kraj/zephyr,Vudentz/zephyr,nashif/zephyr,kraj/zephyr,zephyriot/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,rsalveti/zephyr,mbolivar/zephyr,mbolivar/zephyr,ldts/zephyr,aceofall/zephyr-iotos,fbsder/zephyr,zephyrproject-rtos/zephyr,fbsder/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,zephyriot/zephyr,aceofall/zephyr-iotos,Vudentz/zephyr,aceofall/zephyr-iotos,nashif/zephyr,finikorg/zephyr,nashif/zephyr,rsalveti/zephyr,mbolivar/zephyr,aceofall/zephyr-iotos,mbolivar/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,aceofall/zephyr-iotos,mbolivar/zephyr,ldts/zephyr,punitvara/zephyr,zephyriot/zephyr,runchip/zephyr-cc3220,ldts/zephyr,Vudentz/zephyr,galak/zephyr,runchip/zephyr-cc3220,zephyrproject-rtos/zephyr,kraj/zephyr,fbsder/zephyr,punitvara/zephyr,Vudentz/zephyr,kraj/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,ldts/zephyr,finikorg/zephyr,galak/zephyr,explora26/zephyr,runchip/zephyr-cc3220,nashif/zephyr,ldts/zephyr,punitvara/zephyr,explora26/zephyr,zephyriot/zephyr,fbsder/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyriot/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,runchip/zephyr-cc3220