build_helpers: Fix TC3 default DPE test

The default Attestation scheme for TC3 is DPE but a
reference to tf-m-extras is missing to actually run the
DPE test.

Add it with this patch.

Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
Change-Id: I798bab34dd2f03347eaad98437cb116c3d32b67a
diff --git a/build_helper/build_helper_config_maps.py b/build_helper/build_helper_config_maps.py
index b784a31..5c8e095 100644
--- a/build_helper/build_helper_config_maps.py
+++ b/build_helper/build_helper_config_maps.py
@@ -134,7 +134,10 @@
     "EXTRAS_EXAMPLE_DMA350_CLCD"    : "-DDEFAULT_NS_SCATTER=OFF -DPLATFORM_SVC_HANDLERS=ON ",
 
     "EXTRAS_EXAMPLE_DMA350_S"       : "-DEXTRA_S_TEST_SUITE_PATH=%(codebase_root_dir)s/../tf-m-extras/examples/corstone310_fvp_dma/dma350_s",
-    "EXTRAS_EXAMPLE_DMA350_NS"      : "-DEXTRA_NS_TEST_SUITE_PATH=%(codebase_root_dir)s/../tf-m-extras/examples/corstone310_fvp_dma/dma350_ns"
+    "EXTRAS_EXAMPLE_DMA350_NS"      : "-DEXTRA_NS_TEST_SUITE_PATH=%(codebase_root_dir)s/../tf-m-extras/examples/corstone310_fvp_dma/dma350_ns",
+
+    # Attestation scheme
+    "ATTESTATION_SCHEME_DPE"    : ("-DEXTRA_S_TEST_SUITE_PATH=%(codebase_root_dir)s/../tf-m-extras/partitions/dice_protection_environment/test/secure ")
 }
 
 mapTfmExtrasExamplePaths = {