sh: Kill off machvec aliases.

We now throw all of the machvecs in to .machvec.init and either
select one on the command line, or copy out the first (and
usually only) one to sh_mv. The rest are freed as usual.

This gets rid of all of the silly sh_mv aliasing and makes the
selection explicit rather than link-order dependent.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>