Add number_ios= option

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/thread_options.h b/thread_options.h
index eaafaee..3f345c5 100644
--- a/thread_options.h
+++ b/thread_options.h
@@ -236,6 +236,7 @@
 	unsigned int flow_sleep;
 
 	unsigned long long offset_increment;
+	unsigned long long number_ios;
 
 	unsigned int sync_file_range;
 };
@@ -440,6 +441,7 @@
 	uint32_t flow_sleep;
 
 	uint64_t offset_increment;
+	uint64_t number_ios;
 
 	uint32_t sync_file_range;
 } __attribute__((packed));