Add PNP metadata to more drivers

GPUs: radeonkms, i915kms
NICs: if_em, if_igb, if_bnxt

This metadata isn't used yet, but it will be handy to have later to
implement automatic module loading.

Reviewed by: imp, mmacy
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D12488