examples/vdpa: remove useless device count
examples/vdpa: remove useless device count

The VDPA example now uses the vDPA class iterator, so
knowing the number of available devices beforehand is
no longer needed.

Signed-off-by: Maxime Coquelin <9a2667dee3b90866bbc9c2696cff2b7d5616c95a@redhat.com>
Acked-by: Adrián Moreno <4e5c605993413892a1c21f38afc464bef7695397@redhat.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk