feat(mediatek) : add build configs

Add mt8186 build config.

Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Change-Id: I552015fbc2cc62ee2e1f737d0f773118dd3a550d
diff --git a/tf_config/mt8186-default b/tf_config/mt8186-default
new file mode 100644
index 0000000..1b3d27b
--- /dev/null
+++ b/tf_config/mt8186-default
@@ -0,0 +1,3 @@
+COREBOOT=1
+CROSS_COMPILE=aarch64-none-elf-
+PLAT=mt8186