tests: syscall: Add description and RTM links
tests: syscall: Add description and RTM links

Add description, RTM links and doxygen groups for
syscall test cases

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

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