KVM: Add KVM_MMIO kconfig item

s390 doesn't have mmio, this will simplify ifdefing it out.

Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index 6fb6e8a..be28968 100644
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -20,6 +20,7 @@
 	bool
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
+	select KVM_MMIO
 
 config KVM_BOOK3S_64_HANDLER
 	bool