plat/arm/sgi: reorganize platform macros

In preparation of adding support for upcoming SGI platforms, macros
common to all the SGI platforms are moved into sgi_base_platform_def.h
file. Macros that are specific to sgi575 platform remain in the
platform_def.h file. In addition to this, the platform_def.h file is
moved to sgi575 board directory. Also the ENT_CPU_SOURCES has been
renamed to SGI_CPU_SOURCES and moved from sgi-common.mk to board
specific makefile platform.mk

Change-Id: Iccdd9f070f4feea232b9fbf4fdcc0ef2e8eccbf2
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>
diff --git a/plat/arm/board/sgi575/platform.mk b/plat/arm/board/sgi575/platform.mk
index 078f393..a18e45b 100644
--- a/plat/arm/board/sgi575/platform.mk
+++ b/plat/arm/board/sgi575/platform.mk
@@ -6,9 +6,18 @@
 
 include plat/arm/css/sgi/sgi-common.mk
 
+SGI575_BASE		=	plat/arm/board/sgi575
+
+PLAT_INCLUDES		+=	-I${SGI575_BASE}/include/
+
+SGI_CPU_SOURCES		:=	lib/cpus/aarch64/cortex_a75.S
+
+BL1_SOURCES		+=	${SGI_CPU_SOURCES}
+
 BL2_SOURCES		+=	lib/utils/mem_region.c			\
 				plat/arm/common/arm_nor_psci_mem_protect.c
 
-BL31_SOURCES		+=	drivers/cfi/v2m/v2m_flash.c		\
+BL31_SOURCES		+=	${SGI_CPU_SOURCES}			\
+				drivers/cfi/v2m/v2m_flash.c		\
 				lib/utils/mem_region.c			\
 				plat/arm/common/arm_nor_psci_mem_protect.c