drm/msm/dsi: Enable runtime PM

Some devices power the DSI PHY/PLL through a power rail that we model
as a GENPD. Enable runtime PM to make it suspendable.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/543352/
Link: https://lore.kernel.org/r/20230620-topic-dsiphy_rpm-v2-2-a11a751f34f0@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/dsi/phy/dsi_phy.c

@@ -691,6 +691,10 @@ static int dsi_phy_driver_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(phy->ahb_clk),
 				     "Unable to get ahb clk\n");
 
+	ret = devm_pm_runtime_enable(&pdev->dev);
+	if (ret)
+		return ret;
+
 	/* PLL init will call into clk_register which requires
 	 * register access, so we need to enable power and ahb clock.
 	 */