Add new config-devices.mak for each target

We generate config-devices.h from there automatically.
We need to do it in main Makefile, because we are going to need a main
Makefile for them.

Patchworks-ID: 35196
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/default-configs/sh4eb-softmmu.mak b/default-configs/sh4eb-softmmu.mak
new file mode 100644
index 0000000..2f60e53
--- /dev/null
+++ b/default-configs/sh4eb-softmmu.mak
@@ -0,0 +1 @@
+# Default configuration for sh4eb-softmmu