core-for-CI: drm/i915/mtl: Define GuC firmware version for MTL

Firmware version for MTL is not quite finalized yet, so it's still using the mmp (full) version. We want to add the declaration in the source code to get CI start to run, assess the health of the driver etc.

In theory this could be pushed to drm-intel-gt-next - it's a platform both "not normally enabled" since it's under force-probe and "not generally available publicly. However if the firmware blob is not pushed to the upstream linux-firmware repository, distros may start to see a warning when creating their initrd and the firmware will not be available at the normal place. Also, there isn't much point in going through all the minor and possible major bumps through the upstream firmware repo: it will just unnecessarily increase its size.

So commit in core-for-CI is to get this done for MTL now. For next platforms we will check if we can hide the MODULE_FIRMWARE() under a kconfig so it doesn't cause issues for distros.