boards: silabs: siwx91x: Fix PSRAM half-sleep and external LDO properties

This commit fixes the device tree configuration by adding 'external-ldo'
and 'half-sleep-supported' properties for the PSRAM device, enabling
correct low-power and power source support on siwx917_dk2605a and
siwx917_rb4342a boards.

Signed-off-by: S Mohamed Fiaz <[email protected]>

Author: fimohame

boards/silabs/dev_kits/siwx917_dk2605a/siwx917_dk2605a.dts

@@ -120,6 +120,7 @@ zephyr_i2c: &ulpi2c {
 	device-id = [0d 5d 00 00 00 00 00 00];
 	fast-freq = <DT_FREQ_M(144)>;
 	normal-freq = <DT_FREQ_M(33)>;
+	external-ldo;
 	status = "okay";
 
 	psram: psram@a000000 {

boards/silabs/radio_boards/siwx917_rb4342a/siwx917_rb4342a.dts

@@ -125,6 +125,8 @@
 	device-id = [0d 5d 00 00 00 00 00 00];
 	fast-freq = <DT_FREQ_M(144)>;
 	normal-freq = <DT_FREQ_M(33)>;
+	half-sleep-supported;
+	external-ldo;
 	status = "okay";
 
 	psram: psram@a000000 {