Add support for giving bw/clat/slat log prefixes

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/parse.c b/parse.c
index 8a2e6f2..44c02f6 100644
--- a/parse.c
+++ b/parse.c
@@ -236,7 +236,7 @@
 	dprint(FD_PARSE, "__handle_option=%s, type=%d, ptr=%s\n", o->name,
 							o->type, ptr);
 
-	if (!ptr && o->type != FIO_OPT_STR_SET) {
+	if (!ptr && o->type != FIO_OPT_STR_SET && o->type != FIO_OPT_STR) {
 		fprintf(stderr, "Option %s requires an argument\n", o->name);
 		return 1;
 	}