feat(nxp/layerscape): add build config and variants for ls1046a

Add build config and variants for ls1046a platforms.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>
Change-Id: Ib14a256bc4aa43309a1e62d5760381aa44cf34da
diff --git a/tf_config/ls1046ardb-default b/tf_config/ls1046ardb-default
new file mode 100644
index 0000000..355fa14
--- /dev/null
+++ b/tf_config/ls1046ardb-default
@@ -0,0 +1,2 @@
+CROSS_COMPILE=aarch64-none-elf-
+PLAT=ls1046ardb