Wordsmith mlx4{en,ib}(4)

• Replace the "following lines" with more terse phrases.
• Use .Lk for the mellanox URL.
• Reword the SUPPORT section so it's less wordy.

The DESCRIPTION section suggestions are still outstanding; improving
the section requires additional review to make sure the nuance/message
is correct per the original intent.

Bump .Dd for the change

Submitted by: wblock
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D9241