tests: userspace: Add description and doxygen links
tests: userspace: Add description and doxygen links

Add description and doxygen links to userspace test cases

Signed-off-by: Spoorthi K <c4ff46ff4cba9c2c6c6c9d55497ae534451b4309@intel.com>

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