plat/arm: Skip BL2U if RESET_TO_SP_MIN flag is set

BL2U should not build when RESET_TO_SP_MIN flag is set, like BL1 and
BL2.

Change-Id: Iac516121f98611ca1f58d2b5efdec6525b06ce4e
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>

plat/arm/common/sp_min/arm_sp_min.mk

 #
-# 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
 #
 
 # SP MIN source files common to ARM standard platforms
 
-# Skip building BL1 and BL2 if RESET_TO_SP_MIN flag is set.
+# Skip building BL1, BL2 and BL2U if RESET_TO_SP_MIN flag is set.
 ifeq (${RESET_TO_SP_MIN},1)
     BL1_SOURCES =
     BL2_SOURCES =
+    BL2U_SOURCES =
 endif
 
 BL32_SOURCES		+=	plat/arm/common/arm_pm.c			\
@@ -17,4 +18,3 @@ BL32_SOURCES		+=	plat/arm/common/arm_pm.c			\
 				plat/arm/common/sp_min/arm_sp_min_setup.c	\
 				plat/common/aarch32/platform_mp_stack.S		\
 				plat/common/plat_psci_common.c
-