Makefile: fix implementation of BINMAN_DEBUG

binman only accepts the -D argument early on the command-line, yet the
Makefile currently passes it near the end. This causes the build to fail
if this feature is used. Re-order the command-line to fix this.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>