Move fdt handling logic out of main.c.

This is in preparation for having archs/platforms that don't use FDT.
diff --git a/inc/dlog.h b/inc/dlog.h
index fca8103..1d514a3 100644
--- a/inc/dlog.h
+++ b/inc/dlog.h
@@ -1,12 +1,14 @@
 #ifndef _DLOG_H
 #define _DLOG_H
 
+#include <stdarg.h>
+
 #if DEBUG
 void dlog(const char *fmt, ...);
+void vdlog(const char *fmt, va_list args);
 #else
 #define dlog(...)
+#define vdlog(fmt, args)
 #endif
 
-void dlog_init(void (*pchar)(char));
-
 #endif /* _DLOG_H */