soc: nordic: nrf54l: Set SystemCoreClock using frequency from DT

Use cpu clock source frequency as system core clock.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>

soc/nordic/nrf54l/soc.c

@@ -32,6 +32,7 @@
 
 #include <nrf_erratas.h>
 #include <system_nrf54l.h>
+#include <zephyr/drivers/clock_control/nrf_clock_control.h>
 
 LOG_MODULE_REGISTER(soc, CONFIG_SOC_LOG_LEVEL);
 
@@ -43,9 +44,9 @@ LOG_MODULE_REGISTER(soc, CONFIG_SOC_LOG_LEVEL);
 static int nordicsemi_nrf54l_init(void)
 {
 	/* Update the SystemCoreClock global variable with current core clock
-	 * retrieved from hardware state.
+	 * retrieved from the DT.
 	 */
-	SystemCoreClockUpdate();
+	SystemCoreClock = NRF_PERIPH_GET_FREQUENCY(DT_NODELABEL(cpu));
 
 #if defined(NRF_APPLICATION)
 	/* Enable ICACHE */