feat(intel): add build config and variant for Agilex5

Add build config and variant for Intel Agilex5 platforms.

Signed-off-by: Sieu Mun Tang <sieu.mun.tang@intel.com>
Change-Id: I85fb7eb60d493a95d9a36bba06cbaebf74f9d963
diff --git a/tf_config/agilex5-default b/tf_config/agilex5-default
new file mode 100644
index 0000000..740d380
--- /dev/null
+++ b/tf_config/agilex5-default
@@ -0,0 +1,2 @@
+CROSS_COMPILE=aarch64-none-elf-
+PLAT=agilex5