devicetree: deprecate DT_CLOCKS_LABEL APIs

Mark all variants of the DT_CLOCKS_LABEL APIs:
* DT_CLOCKS_LABEL_BY_IDX
* DT_CLOCKS_LABEL_BY_NAME
* DT_CLOCKS_LABEL
* DT_INST_CLOCKS_LABEL_BY_IDX
* DT_INST_CLOCKS_LABEL_BY_NAME
* DT_INST_CLOCKS_LABEL

As deprecated in favor of utilizing:

* DT_CLOCKS_CTLR_BY_IDX
* DT_CLOCKS_CTLR_BY_NAME
* DT_CLOCKS_CTLR
* DT_INST_CLOCKS_CTLR_BY_IDX
* DT_INST_CLOCKS_CTLR_BY_NAME
* DT_INST_CLOCKS_CTLR

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>