target-ppc: Remove unused kvmppc_read_segment_page_sizes() stub

target-ppc: Remove unused kvmppc_read_segment_page_sizes() stub

This stub function is in the !KVM ifdef in target-ppc/kvm_ppc.h.  However
no such function exists on the KVM side, or is ever used.

I think this originally referenced a function which read host page size
information from /proc, for we we now use the KVM GET_SMMU_INFO extension
instead.

In any case, it has no function now, so remove it.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Alexander Graf <agraf@suse.de>