Based on several reports there is an increasing concern in the impact
of adding additional features to drivers based on compatible strings.
A good example of this situation is found in [1].

In order to reduce this impact and as an initial step for further
reduction, propose a new way to declare compatible strings, which allows
to only include the useful ones.

The idea is to define compatible strings in a way to be easily parsed by
dtoc, which will be responsible to build struct udevice_id [] based on
the compatible strings present in the dtb.

Additional features can be easily added, such as define constants
depending on the presence of compatible strings, which allows to enable
code blocks only in such cases without the need of adding additional
configuration options.

[1] http://patchwork.ozlabs.org/project/uboot/patch/20200525202429.2146-1-agust@denx.de/



Signed-off-by: Walter Lozano <walter.lozano@collabora.com>