Include assert.h in necessary place

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

examples/cpuhog/cpuhog_main.c

@@ -71,6 +71,7 @@
 #include <nuttx/clock.h>
 #include <nuttx/arch.h>
 #include <semaphore.h>
+#include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/stat.h>

wireless/ieee802154/i8sak/i8sak_main.c

@@ -60,6 +60,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <strings.h>
+#include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <queue.h>