drm/msm/dsi: Drop unused regulators from QCM2290 14nm DSI PHY config

The regulator setup was likely copied from other SoCs by mistake.  Just
like SM6125 the DSI PHY on this platform is not getting power from a
regulator but from the MX power domain.

Fixes: 572e9fd6 ("drm/msm/dsi: Add phy configuration for QCM2290")
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/544536/
Link: https://lore.kernel.org/r/20230627-sm6125-dpu-v2-1-03e430a2078c@somainline.org


Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>