GitLab

We use $(call MAKE_TOOL_ARGS,...) or $(call FIP_ADD_IMG,...) where we
expect externally built images.  The difference between the two is
check_* target.  It now checks if the given path exists, so it is a
good thing to use $(call FIP_ADD_IMG,...) in all the places.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>