tests: net: tcp: Remove unnecessary code
tests: net: tcp: Remove unnecessary code

As this test uses dummy L2 driver, there is no need for ethernet
specific setup as that is not used for anything.

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

kraj/zephyr,punitvara/zephyr,zephyriot/zephyr,nashif/zephyr,nashif/zephyr,galak/zephyr,mbolivar/zephyr,punitvara/zephyr,zephyriot/zephyr,finikorg/zephyr,kraj/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,zephyriot/zephyr,Vudentz/zephyr,punitvara/zephyr,Vudentz/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,punitvara/zephyr,explora26/zephyr,kraj/zephyr,mbolivar/zephyr,ldts/zephyr,nashif/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,mbolivar/zephyr,explora26/zephyr,galak/zephyr,zephyriot/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,mbolivar/zephyr,galak/zephyr,nashif/zephyr,kraj/zephyr,Vudentz/zephyr,ldts/zephyr,ldts/zephyr,punitvara/zephyr,galak/zephyr,explora26/zephyr,Vudentz/zephyr,explora26/zephyr,explora26/zephyr,galak/zephyr,zephyriot/zephyr