feat(build): include plat header in fdt build

Include platform headers in DT build to enable build time configuration
of number of execution context supported by the platform.

Signed-off-by: Nishant Sharma <nishant.sharma@arm.com>
Change-Id: I5b9ffc9865f198a1f802fcb5e0950a5fabb48727
diff --git a/Makefile b/Makefile
index f55dfdd..817b16a 100644
--- a/Makefile
+++ b/Makefile
@@ -399,10 +399,6 @@
 
 endif #(LD = armlink)
 
-DTC_FLAGS		+=	-I dts -O dtb
-DTC_CPPFLAGS		+=	-P -nostdinc -Iinclude -Ifdts -undef \
-				-x assembler-with-cpp $(DEFINES)
-
 ################################################################################
 # Setup ARCH_MAJOR/MINOR before parsing arch_features.
 ################################################################################
@@ -444,6 +440,10 @@
 				${PLAT_INCLUDES}			\
 				${SPD_INCLUDES}
 
+DTC_FLAGS		+=	-I dts -O dtb
+DTC_CPPFLAGS		+=	-P -nostdinc $(INCLUDES) -Ifdts -undef \
+				-x assembler-with-cpp $(DEFINES)
+
 include common/backtrace/backtrace.mk
 
 ################################################################################