Add MAX31790 to IPCC inventory

[mkeeter]

The host will eventually want fan tachometer data in its IPCC inventory; this PR adds MAX31790 sensor IDs to our enum InventoryData in preparation.

The new variant is added at the end to preserve existing serialization.

[rmustacc]

This makes sense to me. Thanks, Matt!

[rmustacc]

BRM42220071 # /usr/platform/oxide/bin/ipcc inventory 0x47
metadata:
    version: 0x0
    entries: 0x48
U321 (71) -- Result: 0 [Success]
Type 14, Payload: 0x18 bytes
0000   63 00 00 00 64 00 00 00 65 00 00 00 66 00 00 00  |c...d...e...f...|
0010   67 00 00 00 68 00 00 00                          |g...h...        |

This all appears to be working.