Fix TLSF walker signature

Author: tannewt

ports/raspberrypi/supervisor/port.c

@@ -262,7 +262,7 @@ void *port_realloc(void *ptr, size_t size) {
     return tlsf_realloc(_heap, ptr, size);
 }
 
-static void max_size_walker(void *ptr, size_t size, int used, void *user) {
+static bool max_size_walker(void *ptr, size_t size, int used, void *user) {
     size_t *max_size = (size_t *)user;
     if (!used && *max_size < size) {
         *max_size = size;