Support different log levels.

This will let us add more verbose logs for debugging but have them
compiled out most of the time.

Change-Id: Iaae468e41025a165b5e67fa6fec5422f004c6a44
diff --git a/src/fdt.c b/src/fdt.c
index b046662..85d1d0a 100644
--- a/src/fdt.c
+++ b/src/fdt.c
@@ -386,7 +386,7 @@
 
 	/* Traverse the whole thing. */
 	if (!fdt_root_node(&node, hdr)) {
-		dlog("FDT failed validation.\n");
+		dlog_error("FDT failed validation.\n");
 		return;
 	}