libplatsupport: separate drivers from platforms

[axel-h]

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Many platform use the same peripherals, so code duplication can be avoided if we provide generic drivers.

[kent-mcleod]

Many platform use the same peripherals, so code duplication can be avoided if we provide generic drivers.

The original thought was to use a similar strategy as the kernel does for querying a platform device tree and a configuration file for what compatibility strings to match on and then pulling in source files based on these match strings.

[axel-h]

So, I'd say this PR is a step into that direction then?