Tegra186: trampoline: include bl_common.h

This patch includes bl_common.h from plat_trampoline.S to link with
the __BL31_END__ symbol.

Change-Id: Ie66c5009018472607db668583c9a0b3553f0ae73
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

plat/nvidia/tegra/soc/t186/plat_trampoline.S

 /*
- * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
 #include <arch.h>
 #include <asm_macros.S>
+#include <common/bl_common.h>
 #include <memctrl_v2.h>
 #include <plat/common/common_def.h>
 #include <tegra_def.h>