doc: add vdev ethdev ops restriction in secondary process
doc: add vdev ethdev ops restriction in secondary process

Signed-off-by: Marvin Liu <d89ea4150d91f674af88bbc382d184dd42ea906c@intel.com>
Acked-by: John McNamara <af31595c36a4239b9676e9b3a777d3e2f15a6c4d@intel.com>

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