Only compile isa_mmio when one target uses it

Patchworks-ID: 35200
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/default-configs/arm-softmmu.mak b/default-configs/arm-softmmu.mak
index 15e4373..66834c2 100644
--- a/default-configs/arm-softmmu.mak
+++ b/default-configs/arm-softmmu.mak
@@ -2,3 +2,4 @@
 
 CONFIG_GDBSTUB_XML=y
 CONFIG_USB_OHCI=y
+CONFIG_ISA_MMIO=y