Makefile: refactor include path settings

This commit merges commonly-used header include paths
to UBOOTINCLUDE and NOSTDINC_FLAGS variables, which are placed
at the top Makefile.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/tools/Makefile b/tools/Makefile
index c3cdaf0..21341b7 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -175,11 +175,9 @@
 # Define _GNU_SOURCE to obtain the getline prototype from stdio.h
 #
 HOST_EXTRACFLAGS += -include $(SRCTREE)/include/libfdt_env.h \
-		-idirafter $(SRCTREE)/include \
-		-idirafter $(SRCTREE)/arch/$(ARCH)/include \
-		-idirafter $(OBJTREE)/include \
-		-I $(SRCTREE)/lib/libfdt \
-		-I $(SRCTREE)/tools \
+		$(patsubst -I%,-idirafter%, $(UBOOTINCLUDE)) \
+		-I$(SRCTREE)/lib/libfdt \
+		-I$(SRCTREE)/tools \
 		-DCONFIG_SYS_TEXT_BASE=$(CONFIG_SYS_TEXT_BASE) \
 		-DUSE_HOSTCC \
 		-D__KERNEL_STRICT_NAMES \