options: get rid of more .cb option usage we don't need

- The lat/bw/iops log does not need two ways of storing whether
  they are enabled or not. Just change the option to a string
  storing variant, and use the existance of a filename to see
  if it's set or not.

- The trim_percentage option need not have a callback, the
  parser knows the limits and can store it appropriately.

- The verify_offset option can express it's minimum value
  directly, it doesn't need a callback to set it on its own.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/init.c b/init.c
index aa76733..7422628 100644
--- a/init.c
+++ b/init.c
@@ -842,14 +842,14 @@
 	if (setup_rate(td))
 		goto err;
 
-	if (td->o.write_lat_log) {
+	if (td->o.lat_log_file) {
 		setup_log(&td->lat_log, td->o.log_avg_msec, IO_LOG_TYPE_LAT);
 		setup_log(&td->slat_log, td->o.log_avg_msec, IO_LOG_TYPE_SLAT);
 		setup_log(&td->clat_log, td->o.log_avg_msec, IO_LOG_TYPE_CLAT);
 	}
-	if (td->o.write_bw_log)
+	if (td->o.bw_log_file)
 		setup_log(&td->bw_log, td->o.log_avg_msec, IO_LOG_TYPE_BW);
-	if (td->o.write_iops_log)
+	if (td->o.iops_log_file)
 		setup_log(&td->iops_log, td->o.log_avg_msec, IO_LOG_TYPE_IOPS);
 
 	if (!td->o.name)