new chips and improves support for already supported ones.
Some details, important for future merges:
- if_em.c merged manually, viewing diff between new vendor
driver and previous one.
- if_em_hw.h dropped in from vendor, and then restored revisions
1.16, 1.17, 1.18.
- if_em_hw.c dropped in from vendor, and then two liner change made,
that restores support for two rare chips.