core: correct dt_find_compatible_driver() if no driver found
core: correct dt_find_compatible_driver() if no driver found

By convention the compatible array for driver probing ends with
a NULL compatible string ID reference.

This change ensures such NULL reference is properly handled as
the end of the compatible array references.

Signed-off-by: Etienne Carriere <f21bc5b8f3ea1962eb45af359f1abea6578cab94@linaro.org>
Reviewed-by: Jerome Forissier <ced78d268b4c9a0a20a59a9feeebd2ad90da03d3@linaro.org>

pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os