MINOR: mux-h2: max-concurrent-streams should be unsigned

We compare it to other unsigned values, let's make it unsigned as well.
diff --git a/src/mux_h2.c b/src/mux_h2.c
index 6b4ba61..a811c0a 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -224,7 +224,7 @@
 /* a few settings from the global section */
 static int h2_settings_header_table_size      =  4096; /* initial value */
 static int h2_settings_initial_window_size    = 65535; /* initial value */
-static int h2_settings_max_concurrent_streams =   100;
+static unsigned int h2_settings_max_concurrent_streams = 100;
 
 /* a dmumy closed stream */
 static const struct h2s *h2_closed_stream = &(const struct h2s){
@@ -5424,7 +5424,7 @@
 		return -1;
 
 	h2_settings_max_concurrent_streams = atoi(args[1]);
-	if (h2_settings_max_concurrent_streams < 0) {
+	if ((int)h2_settings_max_concurrent_streams < 0) {
 		memprintf(err, "'%s' expects a positive numeric value.", args[0]);
 		return -1;
 	}