Makefile: targets are now declared phony by the appropriate infrastructures

The main Makefile was declaring a subset of the per-package targets as
being PHONY, but not all of them. Now that the pkg-generic package
infrastructure is taking care of that in a much more systematic
fashion, this commit gets rid of the unneeded code from the main
Makefile.

[Thomas: re-add list-defconfigs to the list of PHONY targets, as
noticed by Yann.]

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

Makefile

@@ -390,7 +390,6 @@ include fs/common.mk
 include $(BR2_EXTERNAL)/external.mk
 
 TARGETS_SOURCE := $(patsubst %,%-source,$(TARGETS))
-TARGETS_DIRCLEAN := $(patsubst %,%-dirclean,$(TARGETS))
 
 # host-* dependencies have to be handled specially, as those aren't
 # visible in Kconfig and hence not added to a variable like TARGETS.
@@ -426,9 +425,7 @@ world: target-post-image
 
 .PHONY: all world toolchain dirs clean distclean source outputmakefile \
 	legal-info legal-info-prepare legal-info-clean printvars help \
-	list-defconfigs target-finalize target-post-image \
-	$(TARGETS) $(TARGETS_ROOTFS) \
-	$(TARGETS_DIRCLEAN) $(TARGETS_SOURCE) $(TARGETS_LEGAL_INFO)
+	list-defconfigs target-finalize target-post-image
 
 ################################################################################
 #