powerpc: Remove old powerpc specific ptrace getregs/setregs calls

PowerPC has non standard getregs calls that only dump the GPRs or
FPRs and have their arguments reversed. commit e17666ba (ptrace
updates & new, better requests) in 2.6.3 deprecated them and introduced
more standard versions.

It's been about 5 years and I know of no users of the old calls so
lets remove them.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>