REORG: include: move lb_chash.h to haproxy/lb_chash{,-t}.h

Nothing fancy, includes were already OK. The proto didn't reference the
type, this was fixed. Still references proxy.h and server.h from types/.
diff --git a/include/types/backend.h b/include/types/backend.h
index 1e2b9df..9f14762 100644
--- a/include/types/backend.h
+++ b/include/types/backend.h
@@ -22,10 +22,10 @@
 #ifndef _TYPES_BACKEND_H
 #define _TYPES_BACKEND_H
 
+#include <haproxy/lb_chash-t.h>
 #include <haproxy/api-t.h>
 #include <haproxy/thread.h>
 
-#include <types/lb_chash.h>
 #include <types/lb_fas.h>
 #include <types/lb_fwlc.h>
 #include <types/lb_fwrr.h>