tools/Makefile: Split variable declarations into multiple lines

Split variable declarations into multiple lines and use the standard
VAR-y convention.  Also move object and binary variable declarations to
after config.mk has been included to allow for these lists to utilize
the CONFIG_XXX variables.

These changes lay the groundwork for conditional compilation of files
in the tools directory.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>