powerpc/configs: Add KVM guest defconfig

This patch adds new defconfig options for powerpc KVM guest
and guest.config with additional config symbols enabled,
which is to build kernel to boot without initramfs and can be used
as place holder for guest specific additional config symbols in future.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>