system/fastboot: Fix Out-of-bounds Write

CID 329130: (apache#3 of 3): 越界写入 (OVERRUN)
6. overrun-local: 在字节偏移 64 处使用索引 r（其值为 64）越界 64 字节访问数组 buffer

Signed-off-by: wangjianyu3 <[email protected]>

system/fastboot/fastboot.c

@@ -847,7 +847,7 @@ static void fastboot_command_loop(FAR struct fastboot_ctx_s *context)
 
   while (1)
     {
-      char buffer[FASTBOOT_MSG_LEN];
+      char buffer[FASTBOOT_MSG_LEN + 1];
       size_t ncmds = nitems(g_fast_cmd);
       size_t index;