Intel update supported platforms

[cujomalainey]

Please update https://thesofproject.github.io/latest/platforms/index.html with MTL now that it is in tree.

Also recommend splitting out legacy platforms and mark where their support ends

[plbossart]

I think it's premature to claim support for a platform which is still in development and without a formal released firmware. Being in the tree and being supported are two separate things.

Conversely for platforms that are no longer in the tree, we should indeed indicate the last supported release.

[cujomalainey]

@plbossart i mean, given hw is not public does it matter? It is more helpful to have that info for early integrators I would think

[plbossart]

It depends what we mean by support. For Intel engineering organization, only the firmware that reach a specific validation status is 'supported'. The rest is considered 'engineering drop' or integration milestones. The general public and distributions would be confused if a device is "supported" but the hardware/firmware not available. It's not helpful. Early integrators have information through partner circles and NDAs, this is the publicly available documentation.

[lgirdwood]

@mwasko we should be able to update this for v2.7