Makefile: convert makefiles to Kbuild style and delete grep switch

We have converted all makefiles needed to build $(LIBS).

Until this commit we used to grep switch so that U-Boot style
and Kbuild style makefiles coexist.
But we do not need any more.

Goint forward, use always Kbuild style Makefile when adding
a new Makefile

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/spl/Makefile b/spl/Makefile
index bf7271d..cbd3d27 100644
--- a/spl/Makefile
+++ b/spl/Makefile
@@ -190,29 +190,12 @@
 $(obj)$(SPL_BIN):	depend $(START) $(LIBS) $(obj)u-boot-spl.lds
 	$(GEN_UBOOT)
 
-# Tentative step for Kbuild-style makefiles coexist with conventional U-Boot style makefiles
-#  U-Boot conventional sub makefiles always include some other makefiles.
-#  So, the build system searches a line beginning with "include" before entering into the sub makefile
-#  in order to distinguish which style it is.
-#  If the Makefile include a "include" line, we assume it is an U-Boot style makefile.
-#  Otherwise, it is treated as a Kbuild-style makefile.
-select_makefile = \
-	if grep -q "^include" $1/Makefile; then				\
-		$(MAKE) -C $1;						\
-	else								\
-		$(MAKE) -C $1 -f $(TOPDIR)/scripts/Makefile.build;	\
-		mv $(dir $@)built-in.o $@;				\
-	fi
-
-# We do not need to build $(START) explicitly.
-# It is built while we are at $(CPUDIR)/lib$(CPU).o build.
-$(START):	depend
-	if grep -q "^include" $(SRCTREE)$(dir $(subst $(SPLTREE),,$@))Makefile; then \
-		$(MAKE) -C $(SRCTREE)/$(START_PATH) $@; \
-	fi
+$(START):
+	@:
 
 $(LIBS):	depend
-	+$(call select_makefile, $(SRCTREE)$(dir $(subst $(SPLTREE),,$@)))
+	$(MAKE) $(build) $(SRCTREE)$(dir $(subst $(SPLTREE),,$@))
+	mv $(dir $@)built-in.o $@
 
 $(obj)u-boot-spl.lds: $(LDSCRIPT) depend
 	$(CPP) $(CPPFLAGS) $(LDPPFLAGS) -I$(obj). -ansi -D__ASSEMBLY__ -P - < $< > $@