sim: m32r: clean up redundant test coverage

sim: m32r: clean up redundant test coverage

The m32r-elf subdir contained three tests:
* exit47: A program to test exit status of 47 from sim.
* hello: Standard "hello world" output program.
* loop: An infinite loop program.

There's already a sim/m32r/hello.ms test that does exactly the same
thing as m32r-elf/hello.s, so we can delete that.

The loop.s test is never referenced anywhere, and is all of 2 lines.
Anyone who really needs a while(1); test case and re-implement it
themselves locally.

That leaves the single exit47 test.  Now that the sim test harness
supports testing for custom exit status, we can easily move that to
sim/m32r/exit47.ms to maintain test coverage.

The remaining differences between m32r-elf & sim/m32r are:
* m32r-elf/ runs for m32r-*-elf while sim/m32r/ runs for m32r*-*-*.
* m32r-elf/ runs "*.s" files while sim/m32r/ runs "*.ms" files.

On closer inspection, these are also meaningless distinctions:
* There is nothing specific to the tests that require an *-elf
  target.  Normally that would mean newlib+libgloss type stuff,
  but there's no such requirement in m32r-elf/.
* The ".s" suffix is the standard "this is an assembly file"
  suffix.  Turns out ".ms" is just how sim/m32r/ (and a few other
  CGEN based targets) categorize/bucket test cases.  It simply
  means "miscellaneous .s" as in "this is an assembly file, and
  run/bucket its test results in the miscellaneous category".

So moving m32r-elf/exit47.s to sim/m32r/exit47.ms makes sense and
simplifies things quite a bit for the target while also slightly
increasing the coverage for some tuples.