Some mellanox housekeeping and a new driver version

[JDarnley]

• An old bugfix was missed in driver version 5.3. I've had this patch for 2 years and I think I tested it at the time but we have moved past that version.
• I discovered that mellanox/nvidia provide a smaller tarball we can download to build netmap that does not bundle large debs. This smaller tarball has the same sha256sum as the first inner tarball of the larger one.
• We are starting to test driver version 5.8 but early tests show no obvious problems with TX or RX. If others want to test it please do.
• We use dkms to package but never shared the "recipe".

[giuseppelettieri]

Looks good, thanks!