arm: add a separate stack for TPL

TPL stack may different from SPL and sys stack, add support for
separate one when the board defines it.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S
index fe312db..30fba20 100644
--- a/arch/arm/lib/crt0.S
+++ b/arch/arm/lib/crt0.S
@@ -67,7 +67,9 @@
  * Set up initial C runtime environment and call board_init_f(0).
  */
 
-#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
+#if defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_NEEDS_SEPARATE_STACK)
+	ldr	r0, =(CONFIG_TPL_STACK)
+#elif defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
 	ldr	r0, =(CONFIG_SPL_STACK)
 #else
 	ldr	r0, =(CONFIG_SYS_INIT_SP_ADDR)