scripts/dtc: consolidate include path options in Makefile

It is tedious to specify extra compiler options for every file.
HOST_EXTRACFLAGS is useful to add options to all files in a
directory.

-I$(src)/libfdt is needed for all the files in this directory
to include libfdt_env.h etc. from scripts/dtc/libfdt/.

On the other hand, -I$(src) is used to include check-in headers
from generated C files.  Thus, I added it only to dtc-lexer.lex.o
and dtc-parser.tab.o .
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Rob Herring <robh@kernel.org>

scripts/dtc/Makefile

@@ -9,21 +9,11 @@ dtc-objs	:= dtc.o flattree.o fstree.o data.o livetree.o treesource.o \
 dtc-objs	+= dtc-lexer.lex.o dtc-parser.tab.o
 
 # Source files need to get at the userspace version of libfdt_env.h to compile
+HOST_EXTRACFLAGS := -I$(src)/libfdt
 
-HOSTCFLAGS_DTC := -I$(src) -I$(src)/libfdt
-
-HOSTCFLAGS_checks.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_data.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_dtc.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_flattree.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_fstree.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_livetree.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_srcpos.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_treesource.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_util.o := $(HOSTCFLAGS_DTC)
-
-HOSTCFLAGS_dtc-lexer.lex.o := $(HOSTCFLAGS_DTC)
-HOSTCFLAGS_dtc-parser.tab.o := $(HOSTCFLAGS_DTC)
+# Generated files need one more search path to include headers in source tree
+HOSTCFLAGS_dtc-lexer.lex.o := -I$(src)
+HOSTCFLAGS_dtc-parser.tab.o := -I$(src)
 
 # dependencies on generated files need to be listed explicitly
 $(obj)/dtc-lexer.lex.o: $(obj)/dtc-parser.tab.h