obmc-console: Clean up invalid sign comparisons

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I83fae6857620ca2913952bea597c1299dd962620
diff --git a/test/test-ringbuffer-contained-offset-read.c b/test/test-ringbuffer-contained-offset-read.c
index 5e41c6a..7490f01 100644
--- a/test/test-ringbuffer-contained-offset-read.c
+++ b/test/test-ringbuffer-contained-offset-read.c
@@ -12,7 +12,8 @@
 	struct ringbuffer_consumer *rbc;
 	struct ringbuffer *rb;
 	size_t len;
-	int rc, i;
+	size_t i;
+	int rc;
 
 	rb = ringbuffer_init(10);
 	rbc = ringbuffer_consumer_register(rb, ringbuffer_poll_nop, NULL);