feat(ti-k3): add build config for J784S4 SoC

Add build config for TI J784S4 SoCs.

Signed-off-by: Hari Nagalla <hnagalla@ti.com>
Change-Id: Ia4748e75825c11fdcfb6448331301c658688846e
diff --git a/tf_config/k3-j784s4-default b/tf_config/k3-j784s4-default
new file mode 100644
index 0000000..a315bea
--- /dev/null
+++ b/tf_config/k3-j784s4-default
@@ -0,0 +1,3 @@
+CROSS_COMPILE=aarch64-none-elf-
+PLAT=k3
+TARGET_BOARD=j784s4