basic: use -EINVAL for _MANAGED_OOM_PREFERENCE_INVALID

Follow-up of #11484

src/basic/cgroup-util.h

@@ -297,7 +297,7 @@ typedef enum ManagedOOMPreference {
         MANAGED_OOM_PREFERENCE_AVOID = 1,
         MANAGED_OOM_PREFERENCE_OMIT = 2,
         _MANAGED_OOM_PREFERENCE_MAX,
-        _MANAGED_OOM_PREFERENCE_INVALID = -1
+        _MANAGED_OOM_PREFERENCE_INVALID = -EINVAL,
 } ManagedOOMPreference;
 
 const char* managed_oom_preference_to_string(ManagedOOMPreference a) _const_;

src/core/dbus-cgroup.c

@@ -1732,7 +1732,7 @@ int bus_cgroup_set_property(
 
                 p = managed_oom_preference_from_string(pref);
                 if (p < 0)
-                        return -EINVAL;
+                        return p;
 
                 if (!UNIT_WRITE_FLAGS_NOOP(flags)) {
                         c->moom_preference = p;