fix intel NIC firmware version detection

frustratingly, ethtool version 5.9 puts commas in the firmware version output with igb cards:

driver: igb
version: 5.10.0-11-amd64
firmware-version: 1.70, 0x80001060, 1.2836.0

this behaviour seems dependent on the network driver, as the same doesn't happen on i40e, e1000e, r8152, r8169, or the various USB and wifi NICs I have tried it on:

driver: i40e
version: 5.10.0-11-amd64
firmware-version: 5.60 0x8000355f 1.1752.0
expansion-rom-version: