doc: create different features files for NFP drivers

doc: create different features files for NFP drivers

NFP PMD implement now PF and VF drivers. Although the driver
functionality is the same by now, except for initialization, it
will change with future PF additions.

A new feature is required for describing the firmware upload
capability coming with the NFP PF now, so the PF file will be
updated soon in another patch.

SRIOV is not supported by the PF yet, and it is wrong to include it
as a VF driver feature, so none of the files have such a feature.

Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
Acked-by: John McNamara <john.mcnamara@intel.com>