interconnect: qcom: icc-rpmh: Get parent's regmap for nested NoCs

Since commit 57eb14779dfd ("interconnect: qcom: icc-rpmh: Support child
NoC device probe") the icc-rpmh driver supports initializing child NoCs,
but those child NoCs also need to be able to get the parent's regmap in
order to enable QoS.

Change the driver to support that and support programming QoS register.

Signed-off-by: Luca Weiss <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Georgi Djakov <[e-mail]>

drivers/interconnect/qcom/icc-rpmh.c

···
 		struct resource *res;
 		void __iomem *base;
 
-		base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
-		if (IS_ERR(base))
-			goto skip_qos_config;
+		/* Try parent's regmap first */
+		qp->regmap = dev_get_regmap(dev->parent, NULL);
+		if (!qp->regmap) {
+			base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+			if (IS_ERR(base))
+				goto skip_qos_config;
 
-		qp->regmap = devm_regmap_init_mmio(dev, base, desc->config);
-		if (IS_ERR(qp->regmap)) {
-			dev_info(dev, "Skipping QoS, regmap failed; %ld\n", PTR_ERR(qp->regmap));
-			goto skip_qos_config;
+			qp->regmap = devm_regmap_init_mmio(dev, base, desc->config);
+			if (IS_ERR(qp->regmap)) {
+				dev_info(dev, "Skipping QoS, regmap failed; %ld\n",
+					 PTR_ERR(qp->regmap));
+				goto skip_qos_config;
+			}
 		}
 
 		qp->num_clks = devm_clk_bulk_get_all(qp->dev, &qp->clks);