Makefile: declare targets PHONY where they are defined

Makefile: declare targets PHONY where they are defined

Currently, a lot of targets are declared PHONY together in the middle
of the Makefile. This has two important shortcomings:

- it is more difficult to see if a target is missing from PHONY;

- it is currently inside the ifeq ($(BR2_HAVE_DOT_CONFIG),y) condition,
  but some of these targets are also defined when there is no .config;
  in that case, these targets are not declared as PHONY.

Both issues can easily be solved by putting the PHONY declaration next
to the definition of the target.

The noconfig_targets are also all declared PHONY together; however,
for these we anyway have to keep the noconfig_targets variable
up-to-date, and that PHONY declaration is outside all conditions, so
there is no benefit of splitting them.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>