powerpc/47x: Split ppc47x machine in two

This machine matches two compatibles and sets .pci_irq_fixup
on one of them.

Split it into two machines, then the probe function can be dropped.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mpe: Drop references to ppc47x_probe() to fix build]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/6cb9865d916231c38401ba34ad1a98c249fae135.1676711562.git.christophe.leroy@csgroup.eu