Update git submodules

* Update docs/submodules/daisy from branch 'master'
  - Merge "add heartbeat interface introduction in docs"
  - add heartbeat interface introduction in docs

    Change-Id: Iaf206f9ea5962410c859ad6f84b03ef1a1aa7771
    Signed-off-by: root <zhou.ya@zte.com.cn>

diff --git a/docs/submodules/daisy b/docs/submodules/daisy
index 77f0857..c255bbb 160000 (submodule)
--- a/docs/submodules/daisy
+++ b/docs/submodules/daisy
@@ -1 +1 @@
-Subproject commit 77f085712a8a7ab2cb42411f457ee87675cdf676
+Subproject commit c255bbbc6ae14ebc4320bb023cb98a31787d8985