make: db_flatstore moved in the standard package

db_flatstore was in db_modules package and ser standard package.
I think it should be removed from db_modules packages as it does
not have any dependencies on db-libraries.

Signed-off-by: Andrei Pelinescu-Onciul <[email protected]>
(cherry picked from commit efaf2651e318574289579730c93d6a73d4734de4)

Makefile

@@ -156,7 +156,7 @@ module_group_standard_dep=acc_db acc_radius auth_db auth_radius avp_db \
 				presence_b2b rls speeddial uri_db xcap xmlrpc
 
 # For db use (db modules, excluding drivers)
-module_group_db=acc_db auth_db avp_db db_ops db_flatstore db_text \
+module_group_db=acc_db auth_db avp_db db_ops db_text \
 				uri_db domain lcr msilo speeddial
 				#dbtext (s) not migrated yet to the new db interface