imx8mp: phyboard-pollux-rdk: Convert to DM_PMIC

Convert the board to use DM_PMIC instead of the legacy SPL I2C/PMIC
handling.

Changes include:
- Enable DM_PMIC, DM_PMIC_PCA9450, and SPL_DM_PMIC_PCA9450 in defconfig.
- Drop legacy SPL I2C and PMIC options.
- Remove manual I2C1 pad setup and legacy power_pca9450_init() usage.
- Use DM-based pmic_get() with the DT node "pmic@25".
- Update PMIC register programming to use struct udevice API.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Yannic Moog <y.moog@phytec.de>
Tested-by: Yannic Moog <y.moog@phytec.de>
Reviewed-by: Teresa Remmet <t.remmet@phytec.de>

arch/arm/dts/imx8mp-phyboard-pollux-rdk-u-boot.dtsi

@@ -34,6 +34,18 @@
 	};
 };
 
+&pinctrl_i2c1 {
+	bootph-all;
+};
+
+&pinctrl_pmic {
+	bootph-all;
+};
+
+&{/soc@0/bus@30800000/i2c@30a20000/pmic@25/regulators} {
+	bootph-all;
+};
+
 &reg_usdhc2_vmmc {
 	bootph-pre-ram;
 };
@@ -83,11 +95,11 @@
 };
 
 &i2c1 {
-	bootph-pre-ram;
+	bootph-all;
 };
 
 &pmic {
-	bootph-pre-ram;
+	bootph-all;
 };
 
 &usb_dwc3_0 {
@@ -96,6 +108,12 @@
 
 &usdhc2 {
 	bootph-pre-ram;
+	/*
+	 * LDO5 output depends on SD2_VSEL, but no way to read back SD2_VSEL
+	 * when using SDHC controller VSELECT to control SD2_VSEL. So drop
+	 * vqmmc-supply to avoid fsl_esdhc_imx read back wrong voltage.
+	 */
+	/delete-property/ vqmmc-supply;
 };
 
 &usdhc3 {