powerpc: Start using ___PPC_RA/B/S/T where necessary

Now have ___PPC_RA/B/S/T we can use it in some places.  These are
places where we can't use the existing defines which will soon enforce
R0-R31 usage.

The macros being changed here are being used in inline asm, which
can't convert to enforce the R0-R31 usage.

bpf_jit uses a mix of both generated and non-generated with the same
code, so just convert all these to use the ___PPC_R versions which
won't enforce R usage later.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>