heap fixup

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

zephyr/include/rtos/alloc.h

@@ -141,6 +141,10 @@ static inline void heap_trace_all(int force) {}
 
 #if CONFIG_SOF_USERSPACE
 
+/**
+ * Returns whether pointer is in userspace heap.
+ * @return True is userspace pointer.
+ */
 bool s_heap_user_is_pointer(void *ptr);
 
 /**