plat/arm: Remove board/ directory

The board/ directory does not actually bring any benefit. There's no
need to separate the board level from any other level. Thus, this
patch flattens the Arm platform tree like so:

plat/arm/
|- common
|- fvp
|- juno
|- sgi
|   |- common
|   |- sgi575

Change-Id: I10e4af7594bb555d912222a881d95eae9864637e
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
diff --git a/plat/arm/sgi/sgi575/platform.mk b/plat/arm/sgi/sgi575/platform.mk
new file mode 100644
index 0000000..8472d7e
--- /dev/null
+++ b/plat/arm/sgi/sgi575/platform.mk
@@ -0,0 +1,13 @@
+#
+# Copyright (c) 2018, Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+include plat/arm/sgi/common/sgi_common.mk
+
+PLAT_INCLUDES		+=	-Iplat/arm/sgi/sgi575/include/
+
+PLAT_SOURCES		+=	plat/arm/sgi/sgi575/sgi575_topology.c
+
+PLAT_TESTS_SKIP_LIST	:=	plat/arm/sgi/sgi575/tests_to_skip.txt