bankd: Initialize logging early.

In case libosmocore wants to log e.g. a failure to bind the port,
we must have initialized logging before that point.

Change-Id: I86e805a66da6269748e6bd3164e5c0342e014f77
diff --git a/src/bankd.h b/src/bankd.h
index 3577d15..21d0ccb 100644
--- a/src/bankd.h
+++ b/src/bankd.h
@@ -14,6 +14,10 @@
 
 #include "rspro_util.h"
 
+enum {
+	DMAIN,
+};
+
 struct bankd;
 
 struct bank_slot {