tests/net: Reducing utils test by removing redundant ones
tests/net: Reducing utils test by removing redundant ones

The very first test was basically testing the checksum calculation. And
that's already tested in more relevant tests. It was also trying in a
cumbersome way to generate packets scattered over many net_buf. But
that's also already tested in various other tests, and it's not at all
part of core utils anyway.

In any case, that all redundant, so let's remove it.

Signed-off-by: Tomasz Bursztyka <ba81a3a719836727e6857ae83462b9f52ec41006@linux.intel.com>

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