Add the following macro's to get clock info by name:
DT_CLOCKS_LABEL_BY_NAME
DT_CLOCKS_CELL_BY_NAME
DT_INST_CLOCKS_LABEL_BY_NAME
DT_INST_CLOCKS_CELL_BY_NAME
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
Co-Authored-By: Marti Bolivar <marti.bolivar@nordicsemi.no>