tests: coverage: fix test cases failed with code coverage in mps2_an385
tests: coverage: fix test cases failed with code coverage in mps2_an385

This only fix several test cases failed while running code coverage
report inmps2_an385 platform. Enlarge the stack size for which failed
due to MPU fault of stack overflow.

Signed-off-by: Enjia Mai <233e651694b7770d0f980a273a8e4a6f7e2a84d4@intel.com>

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