examples: remove legacy sections of makefiles

examples: remove legacy sections of makefiles

The example app makefiles contained sections using the legacy method of
compiling with make. These are no longer needed, and are removed,
leaving only the section that uses pkg-config for the make build.

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Nicolas Chautru <nicolas.chautru@intel.com>