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/boot_flow/linux.c b/src/boot_flow/linux.c
index e1e257c..a3dff65 100644
--- a/src/boot_flow/linux.c
+++ b/src/boot_flow/linux.c
@@ -63,8 +63,8 @@
 	if (string_is_empty(filename)) {
 		memiter_init(&primary_initrd, NULL, 0);
 	} else if (!cpio_get_file(cpio, filename, &primary_initrd)) {
-		dlog("Unable to find primary initrd \"%s\".\n",
-		     string_data(filename));
+		dlog_error("Unable to find primary initrd \"%s\".\n",
+			   string_data(filename));
 		return false;
 	}