conform.yaml: update to coreboot guidelines

[macpijan]

Change first line of commit message from 80 to 75.

Set the commit body as required.

Source: https://doc.coreboot.org/contributing/gerrit_guidelines.html#commit-message-guidelines

Change-Id: Iaab7a6a2c4adffa6b04b170b94cc98f3b157558e

[macpijan]

Testing if it works as expected.

This conform tool should allow us to check if commit body exists.

For the Upstream-Status tag we would likely need a separate hook.

[macpijan]

Ok, the body check does not work for me, at least the way I would expect. Need to check.

EDIT:

OK I guess it's due to the Gerrit hooks adding: Change-Id: Iaab7a6a2c4adffa6b04b170b94cc98f3b157558e.

So we would need to modify this tool to add some more exceptions, preferably configurable via config file. Currently, it drops the DCO (Signed-off) line from this check only.