[CSA-CP]Fix GFW image build with ProvisionStorageFlash option (#375)

Author: jmartinez-silabs

examples/platform/silabs/provision/ProvisionStorageFlash.cpp

@@ -29,7 +29,7 @@
 #include <platform/silabs/multi-ota/OtaTlvEncryptionKey.h>
 #endif // OTA_ENCRYPTION_ENABLE
 
-#if !SL_MATTER_GN_BUILD
+#if !(SL_MATTER_GN_BUILD || defined(SL_PROVISION_GENERATOR))
 #include <sl_matter_provision_config.h>
 #endif