still building soft-fp on ppclinux

[Jack Howarth]

Aldy,
   Forget about my suggestion of merging the common files
together. That will never work because the two different
libm-test-ulps can never be merged. I guess that leaves us
stuck with hacking the build so that the appearance of
paths sysdeps/powerpc/fpu and sysdeps/powerpc/soft-fp in
config-sysdirs of config.make depends on the setting of
completely_soft.
                      Jack