phy: qcom-qmp-combo: add dedicated DP iomem pointers

In preparation for merging the driver data, add separate iomem pointers
for the DP part of the PHY.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20221114110621.4639-14-johan+linaro@kernel.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>