Remove unneeded include paths in PLAT_INCLUDES

Also, update platform_def.h guidelines about includes in the porting
guide.

Change-Id: I1ae338c9dd3242b309f6d53687ba2cb755d488c3
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/hisilicon/hikey/platform.mk b/plat/hisilicon/hikey/platform.mk
index 6d077f7..99887ee 100644
--- a/plat/hisilicon/hikey/platform.mk
+++ b/plat/hisilicon/hikey/platform.mk
@@ -45,8 +45,7 @@
 
 USE_COHERENT_MEM	:=	1
 
-PLAT_INCLUDES		:=	-Iinclude/common/tbbr			\
-				-Iplat/hisilicon/hikey/include
+PLAT_INCLUDES		:=	-Iplat/hisilicon/hikey/include
 
 PLAT_BL_COMMON_SOURCES	:=	drivers/arm/pl011/aarch64/pl011_console.S \
 				lib/xlat_tables/aarch64/xlat_tables.c	\