ms4: add ms4

ms4/Makefile

ms4/README.md

ms4/accel-sim/dma.c

ms4/accel-sim/plumbing.c

ms4/accel-sim/plumbing.h

ms4/accel-sim/sim.c

ms4/accel-sim/sim.h

ms4/app/driver.c

ms4/app/driver.h

ms4/app/matmul-accel.c

ms4/common/reg_defs.h

ms4/tests/check_common.py

ms4/tests/hwaccel_common.py

ms4/tests/test0.check.py

ms4/tests/test0.sim.py

ms4/tests/test1.check.py

ms4/tests/test1.sim.py