examples: put app name and sources at top of makefiles

examples: put app name and sources at top of makefiles

Reorder the text in the makefiles, so that the app name and the source
files are listed first. This then will allow them to be shared later in a
combined makefile building with pkg-config and RTE_SDK-based build system.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: Luca Boccassi <bluca@debian.org>