mlx5/mlx4: Bump driver version to 3.7
While at it only output driver version to dmesg(8) when hardware is present.
Differential Revision: https://reviews.freebsd.org/D29100
MFC after: 1 week
Reviewed by: kib and markj
Sponsored by: NVIDIA Networking
(cherry picked from commit d2cbfbc57b20700d6eb04dbfc4d636ce6c92997c)