Build: merge build macros between FIP_ and FWU_FIP_

The build system supports generating two FIP images, fip and fwu_fip.
Accordingly, we have similar build macros.

   FIP_ADD_PAYLOAD   <-->  FWU_FIP_ADD_PAYLOAD
   CERT_ADD_CMD_OPT  <-->  FWU_CERT_ADD_CMD_OPT
   FIP_ADD_IMG       <-->  FWU_FIP_ADD_IMG

The duplicated code increases the maintenance burden.  Also, the build
rule of BL2U looks clumsy - we want to call MAKE_BL to compile it from
source files, but we want to put it in fwu_fip.  We can not do it in a
single macro call since the current MAKE_BL does not support fwu_fip.

To refactor those in a clean way is to support one more argument to
specify the FIP prefix.  If it is empty, the images are targeted to
fip, whereas if the argument is "FWU_", targeted to fwu_fip.

The build macros prefixed with FWU_ go away.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/plat/arm/css/common/css_common.mk b/plat/arm/css/common/css_common.mk
index 63e3059..4232a44 100644
--- a/plat/arm/css/common/css_common.mk
+++ b/plat/arm/css/common/css_common.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -49,7 +49,7 @@
 ifeq (${CSS_LOAD_SCP_IMAGES},1)
   NEED_SCP_BL2 := yes
   ifneq (${TRUSTED_BOARD_BOOT},0)
-    $(eval $(call FWU_FIP_ADD_IMG,SCP_BL2U,--scp-fwu-cfg))
+    $(eval $(call FIP_ADD_IMG,SCP_BL2U,--scp-fwu-cfg,FWU_))
   endif
 
   ifeq (${CSS_USE_SCMI_SDS_DRIVER},1)