plat/hikey: boot memory layout to dedicated file

Boot memory layout is specific for a platform, but should not be
mixed up with other platform specific attributes. A separate file is
much cleaner and better to compare with other platforms. Take a look
at plat/poplar where it is done the same way.

Moved hikey_def.h to system include folder and moved includes from
hikey_def.h to more general platform_def.h.

Signed-off-by: Michael Brandl <git@fineon.pw>
diff --git a/plat/hisilicon/hikey/hikey_bl2_mem_params_desc.c b/plat/hisilicon/hikey/hikey_bl2_mem_params_desc.c
index 7c025c3..23c16ed 100644
--- a/plat/hisilicon/hikey/hikey_bl2_mem_params_desc.c
+++ b/plat/hisilicon/hikey/hikey_bl2_mem_params_desc.c
@@ -7,7 +7,7 @@
 #include <bl_common.h>
 #include <desc_image_load.h>
 #include <platform.h>
-#include <platform_def.h>
+#include <platform_def.h>	/* also includes hikey_def.h and hikey_layout.h*/
 
 
 /*******************************************************************************