powerpc: select ARCH_MIGHT_HAVE_PC_PARPORT

Architectures which support CONFIG_PARPORT_PC should select
ARCH_MIGHT_HAVE_PC_PARPORT.

Signed-off-by: Mark Salter <msalter@redhat.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: linuxppc-dev@lists.ozlabs.org