Remove sysdeps/powerpc/soft-fp directory.

Remove sysdeps/powerpc/soft-fp directory.

As per <https://sourceware.org/ml/libc-alpha/2014-10/msg00369.html>,
there should not be separate sysdeps/<arch>/soft-fp directories when
those are used by all configurations that use sysdeps/<arch>, and,
more generally, should not be sysdeps/foo/Implies files pointing to a
subdirectory foo/bar.

sysdeps/powerpc/soft-fp isn't quite such a case, as the Implies files
pointing to it are
sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/Implies and
sysdeps/unix/sysv/linux/powerpc/powerpc32/e500/nofpu/Implies (and
indeed there is a different sfp-machine.h used for powerpc64le).
However, the same principle applies: there is no need for this
directory because sfp-machine.h, the only file in it, can most
naturally go in sysdeps/powerpc/nofpu, which is used by exactly the
same configurations (and there is a close dependence between the files
there and the sfp-machine.h implementation).  This patch eliminates
the sysdeps/powerpc/soft-fp directory accordingly.

Tested with build-many-glibcs.py that installed stripped shared
libraries for powerpc configurations are unchanged by this patch.

	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/Implies: Remove
	powerpc/soft-fp.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/e500/nofpu/Implies:
	Likewise.
	* sysdeps/powerpc/soft-fp/sfp-machine.h: Move to ....
	* sysdeps/powerpc/nofpu/sfp-machine.h: ... here.