util: fix a printf format

revert a mistake in commit 34582733.
("Avoid printf type modifiers not supported by MSVC C runtime library.")

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Jesse Gross <jesse@nicira.com>

lib/util.c

@@ -346,7 +346,7 @@ ovs_strerror(int error)
          * is too short).  We don't check the actual failure reason because
          * POSIX requires strerror_r() to return the error but old glibc
          * (before 2.13) returns -1 and sets errno. */
-        snprintf(buffer, BUFSIZE, "Unknown error %"PRIuSIZE, error);
+        snprintf(buffer, BUFSIZE, "Unknown error %d", error);
     }
 #endif