sim: bfin: speed up all insn testcases slightly

sim: bfin: speed up all insn testcases slightly

The main body of the "all insn" test is executed once per tested insn, and
we test millions of insns here.  Any shrinkage we can do in this loop will
speed things up nicely (since it's multiplied per tested insn).

To that end, simplify the end-of-table test into one less insn, and omit
the SSYNC when we build for the sim.  When we build to run on the hardware,
this insn matters, but the sim doesn't have write store buffers in the chip
that might get in the way (memory writes are atomic).