SGI: Include arm_spm_def.h in platform_def.h

Include arm_spm_def.h in the platform_def.h file. Without this
inclusion, we get build errors like

In file included from services/std_svc/spm/sp_setup.c:12:0:
services/std_svc/spm/sp_setup.c: In function 'spm_sp_setup':
services/std_svc/spm/sp_setup.c:61:57: error: 'PLAT_SPM_BUF_BASE'
  undeclared (first use in this function)
  write_ctx_reg(get_gpregs_ctx(ctx), CTX_GPREG_X0, PLAT_SPM_BUF_BASE);

Now that the platform_def.h includes arm_spm_def.h, remove inclusion
of platform_def.h in arm_spm_def.h to remove the circular dependency.

Change-Id: I5225c8ca33fd8d288849524395e436c3d56daf17
Signed-off-by: Sughosh Ganu <sughosh.ganu@arm.com>
diff --git a/include/plat/arm/common/arm_spm_def.h b/include/plat/arm/common/arm_spm_def.h
index 83277a6..3d7ded2 100644
--- a/include/plat/arm/common/arm_spm_def.h
+++ b/include/plat/arm/common/arm_spm_def.h
@@ -7,7 +7,6 @@
 #define __ARM_SPM_DEF_H__
 
 #include <arm_def.h>
-#include <platform_def.h>
 #include <utils_def.h>
 #include <xlat_tables_defs.h>
 
diff --git a/plat/arm/css/sgi/include/platform_def.h b/plat/arm/css/sgi/include/platform_def.h
index 7a2a6bd..3230ca8 100644
--- a/plat/arm/css/sgi/include/platform_def.h
+++ b/plat/arm/css/sgi/include/platform_def.h
@@ -8,6 +8,7 @@
 #define PLATFORM_DEF_H
 
 #include <arm_def.h>
+#include <arm_spm_def.h>
 #include <board_arm_def.h>
 #include <board_css_def.h>
 #include <common_def.h>