Ensuring EntityManager starts before all Sensor services

This fix was needed by PSUSensor
However, all of these Sensor services are written in a similar way
All could probably benefit from this similar fix
Adds Requires and After for EntityManager
Also clean up dangling Requires that did not have After
Tested: On PSUSensor only

Signed-off-by: Josh Lehan <krellan@google.com>
Change-Id: Ib132b642b88dfb344b28d27d55dfd89b49e917f4
diff --git a/service_files/xyz.openbmc_project.fansensor.service b/service_files/xyz.openbmc_project.fansensor.service
index 8e24781..f452ebf 100644
--- a/service_files/xyz.openbmc_project.fansensor.service
+++ b/service_files/xyz.openbmc_project.fansensor.service
@@ -1,6 +1,8 @@
 [Unit]
 Description=Fan Sensor
 StopWhenUnneeded=false
+Requires=xyz.openbmc_project.EntityManager.service
+After=xyz.openbmc_project.EntityManager.service
 
 [Service]
 Restart=always