meta-facebook: yosemite4: Fix sled cycle fail on dvt

Since the stage information is obtained from the entity manager.
Modify the init service to run after the entity manager.

Tested:
Did sled cycle on EVT, DVT an PVT system.

Change-Id: I16cdad5397dc4ca581a7ab40dc1eb95fe40b3089
Signed-off-by: Marshall Zhan <marshall.zhan.wiwynn@gmail.com>
diff --git a/meta-facebook/meta-yosemite4/recipes-yosemite4/plat-svc/files/yosemite4-schematic-init b/meta-facebook/meta-yosemite4/recipes-yosemite4/plat-svc/files/yosemite4-schematic-init
index e254977..ff17e07 100644
--- a/meta-facebook/meta-yosemite4/recipes-yosemite4/plat-svc/files/yosemite4-schematic-init
+++ b/meta-facebook/meta-yosemite4/recipes-yosemite4/plat-svc/files/yosemite4-schematic-init
@@ -2,6 +2,10 @@
 # shellcheck source=meta-facebook/meta-yosemite4/recipes-yosemite4/plat-tool/files/yosemite4-common-functions
 source /usr/libexec/yosemite4-common-functions
 
+# wait for entity manager
+mapper wait /xyz/openbmc_project/inventory/system/board/Yosemite_4_Management_Board
+mapper wait /xyz/openbmc_project/inventory/system/board/Yosemite_4_Medusa_Board
+
 # probe devices behind mux for management board cpld
 mgm_stage=$(get_product_version Management_Board)