Separate the devicetree parsing of the USB and DP child nodes in two
dedicated helpers in preparation for merging the driver data.

Note that only the USB part of the PHY has a pipe clock and that the DP
implementation only uses the tx/tx2 and pcs register regions.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20221114110621.4639-13-johan+linaro@kernel.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>