refactor(Makefile): move NEED_<IMAGE> before their use

In later patch tbbr_tools.mk requires NEED_BL2 definition which is
defined after inclusion of this mk file.
Move NEED_<IMAGE> definitions earlier to their use

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Ieff999b255690755779d0cd35d5aba2d3794873c
1 file changed