x86: Compile xen-pci-frontend as module

modified version of -> http://patchwork.openwrt.org/patch/5535/

Signed-off-by: John Crispin <blogic@openwrt.org>

SVN-Revision: 40947

target/linux/x86/xen_domu/config-3.10

@@ -69,7 +69,7 @@ CONFIG_XEN_GRANT_DEV_ALLOC=m
 CONFIG_XEN_HAVE_PVMMU=y
 CONFIG_XEN_MAX_DOMAIN_MEMORY=64
 # CONFIG_XEN_NETDEV_FRONTEND is not set
-CONFIG_XEN_PCIDEV_FRONTEND=y
+# CONFIG_XEN_PCIDEV_FRONTEND is not set
 CONFIG_XEN_PRIVCMD=m
 # CONFIG_XEN_PRIVILEGED_GUEST is not set
 CONFIG_XEN_PVHVM=y