Enable Yocto control of the USING_ENTITY_MANAGER_DECORATORS

The USING_ENTITY_MANAGER_DECORATORS compile switch is hard coded to
enabled in a header file. The changes here allow the feature to be
controlled in recipes via PACKAGECONFIG entries in bbappend files.

Tested:
Applied https://gerrit.openbmc.org/c/openbmc/openbmc/+/63434
Modified internal bbappend file to PACKAGECONFIG:remove
entity-manager-decorators
Confirmed the code guarded by the ifdef no longer compiled
Removed change to bbappend file
Confirmed the code guarded by the ifdef was restored.

Change-Id: I4f3072451f893fcb5edaa478d0546253e7005b9f
Signed-off-by: Johnathan Mantey <johnathanx.mantey@intel.com>
diff --git a/meson_options.txt b/meson_options.txt
index aa21246..59c597f 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -49,6 +49,9 @@
 option('ipmi-whitelist', type: 'feature', description: 'Enable/disable IPMI whitelist filtering')
 option('whitelist-conf', type: 'string', value: 'host-ipmid-whitelist.conf', description: 'Paths to IPMI whitelisted commands conf files')
 
+# Entity Manager Decorators
+option('entity-manager-decorators', type: 'feature', value: 'enabled', description: 'The Entity Manager Decorators flag is enabled by default; offer a way to disable it')
+
 # Dynamic Sensor Stack
 option('dynamic-sensors', type: 'feature', value: 'disabled', description: 'Dynamic sensors stack is enabled by default; offer a way to disable it')
 option('dynamic-sensors-write', type: 'feature', value: 'disabled', description: 'Dynamic sensors stack is enabled by default; offer a way to disable it')