[nrf fromtree] dts: nordic: Add wifi_spi label

Add wifi_spi label to nRF54h and nRF54l dts files to help
in shield overlay files

Signed-off-by: Bansidhar P.M <[email protected]>
(cherry picked from commit eb93df2)

Author: bama-nordic

boards/nordic/nrf54h20dk/nrf54h20dk_nrf54h20-common.dtsi

@@ -16,3 +16,6 @@
 &lfxo {
 	status = "okay";
 };
+
+/* Get a node label for wi-fi spi to use in shield files */
+wifi_spi: &spi130 {};

boards/nordic/nrf54l15dk/nrf54l15dk_common.dtsi

@@ -98,3 +98,6 @@
 	pinctrl-1 = <&pwm20_sleep>;
 	pinctrl-names = "default", "sleep";
 };
+
+/* Get a node label for wi-fi spi to use in shield files */
+wifi_spi: &spi22 {};