Enter error state when handling bad device in mlx5core and add checks
for error state to mlx5en(4) to make live migration work.

This is a direct commit.

Sponsored by: Mellanox Technologies

MFC r312881:
Add support for device surprise removal and other PCI errors.

- When device disappears from PCI indicate error device state and:
1) Trigger command completion for all pending commands
2) Prevent new commands from executing and return:
- success for modify and remove/cleanup commands
- failure for create/query commands
3) When reclaiming pages for a device in error state don't ask FW to
return all given pages, just release the allocated memory

Sponsored by: Mellanox Technologies

MFC r290650, r290709, r291067, r291068, r291069 and r291070:
Add mlx5 and mlx5en driver(s) for ConnectX-4 and ConnectX-4LX cards
from Mellanox Technologies. The current driver supports ethernet
speeds up to and including 100 GBit/s. Infiniband support will be
done later.

The code added is not compiled by default, which will be done by a
separate commit.

Sponsored by: Mellanox Technologies
Differential Revision: https://reviews.freebsd.org/D4177
Differential Revision: https://reviews.freebsd.org/D4178
Differential Revision: https://reviews.freebsd.org/D4179
Differential Revision: https://reviews.freebsd.org/D4180