fix warning: format specifies type 'int' but the argument has type 'size_t' (aka 'unsigned long')

Bug: None
Test: The warning is gone.
Change-Id: Icd04c116d67c1841b02a6242fa6a7a1681404837
diff --git a/recovery/oem-recovery/dec.cpp b/recovery/oem-recovery/dec.cpp
index a8b1d2c..ab4e190 100644
--- a/recovery/oem-recovery/dec.cpp
+++ b/recovery/oem-recovery/dec.cpp
@@ -302,7 +302,7 @@
     }
     fflush(file);
     fclose(file);
-    fprintf(stdout, "%s written %d bytes\n", fname, len);
+    fprintf(stdout, "%s written %zu bytes\n", fname, len);
     return 0;
 }