client: fix missing pdu->log_offset endianness conversion

Make the iolog sample number uint64_t as well, so we have
the same size across 32 and 64-bit archs.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/iolog.h b/iolog.h
index b387f48..eed9297 100644
--- a/iolog.h
+++ b/iolog.h
@@ -48,8 +48,8 @@
 	/*
 	 * Entries already logged
 	 */
-	unsigned long nr_samples;
-	unsigned long max_samples;
+	uint64_t nr_samples;
+	uint64_t max_samples;
 	void *log;
 
 	unsigned int log_type;