powerpc/configs/64s: Enable DEBUG_VM & other options

Fedora enables DEBUG_VM, which has led to occasions where a VM_BUG_ON()
is not caught by upstream testing, but rather is first found in Fedora,
which is not how it's meant to be.

PAGE_OWNER & PAGE_POISONING both need to be enabled on the kernel
command line, so should not add much overhead in normal operation.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230414132415.821564-20-mpe@ellerman.id.au