doc: postpone devargs genericisation notice
doc: postpone devargs genericisation notice

Device querying and declaration has been postponed to 18.08.
Additionally, while working on the feature, some changes previously
announced won't be enacted.

Signed-off-by: Gaetan Rivet <a6b9f1aecd7707f01344f211143eb3bcaeb0c5c3@6wind.com>

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