boards: arduino: fix long startup time with WIFI enabled

The default SDHC 'power-delay-ms' is 500 ms, which is unnecessarily long
and causes the boot time to increase by over 5 seconds on H7 boards with
the Murata Wi-Fi card (GIGA R1, Nicla Vision, Portenta H7).

Shortening this delay to 50 ms greatly improves boot time while keeping
compatibility with the controller spec.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>

Author: pillo79

boards/arduino/giga_r1/arduino_giga_r1.dtsi

@@ -56,6 +56,7 @@ sdhc: &sdmmc1 {
 			&sdmmc1_ck_pc12 &sdmmc1_cmd_pd2>;
 	pinctrl-names = "default";
 	sdhi-on-gpios = <&gpiob 10 GPIO_ACTIVE_HIGH>;
+	power-delay-ms = <50>;
 	min-bus-freq = <DT_FREQ_K(400)>;
 	max-bus-freq = <DT_FREQ_M(208)>;
 	hw-flow-control;

boards/arduino/nicla_vision/arduino_nicla_vision.dtsi

@@ -45,6 +45,7 @@ sdhc: &sdmmc2 {
 			&sdmmc2_ck_pd6 &sdmmc2_cmd_pd7>;
 	pinctrl-names = "default";
 	sdhi-on-gpios = <&gpiog 4 GPIO_ACTIVE_HIGH>;
+	power-delay-ms = <50>;
 	min-bus-freq = <DT_FREQ_K(400)>;
 	max-bus-freq = <DT_FREQ_M(208)>;
 	hw-flow-control;

boards/arduino/portenta_h7/arduino_portenta_h7-common.dtsi

@@ -247,6 +247,7 @@ sdhc: &sdmmc1 {
 			&sdmmc1_ck_pc12 &sdmmc1_cmd_pd2>;
 	pinctrl-names = "default";
 	sdhi-on-gpios = <&gpioj 1 GPIO_ACTIVE_HIGH>;
+	power-delay-ms = <50>;
 	interrupts = <49 0>;
 	interrupt-names = "event";
 	min-bus-freq = <DT_FREQ_K(400)>;