boards/qemu_cortex_m3: Use SCHED_MULTIQ by default
boards/qemu_cortex_m3: Use SCHED_MULTIQ by default

Have qemu_cortex_m3 use the traditional multiqueue scheduler by
default, to be sure it gets test coverage.

Signed-off-by: Andy Ross <c70f9a6bf6ee0cd69c8af4ce5e6b131945769315@intel.com>

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