[nrf noup] boards: nordic: nrf54l15dk: Set MPSL_HFCLK_LATENCY default

This default matches the default before it got changed in
nrfconnect/sdk-nrf#22369. This ensures
that the current consumption when using Bluetooth remains unchanged.

The default of 854 is likely good enough for this board.

This noup commit can be replaced once:
* HFXO startup latency is defined in device tree:
  zephyrproject-rtos/zephyr#90615
* The startup latency is configured per board and not per SoC.
  The startup latency is board specific as the HFXO is an SOC-external
  component.

Signed-off-by: Rubin Gerritsen <rubin.gerritsen@nordicsemi.no>

Author: rugeGerritsen

boards/nordic/nrf54l15dk/Kconfig.defconfig

@@ -5,6 +5,11 @@
 DT_CHOSEN_Z_CODE_PARTITION := zephyr,code-partition
 DT_CHOSEN_Z_SRAM_PARTITION := zephyr,sram-secure-partition
 
+# The 54L has a HFXO latency which is better than the default.
+config MPSL_HFCLK_LATENCY
+	int
+	default 854 if MPSL
+
 if BOARD_NRF54L15DK_NRF54L05_CPUAPP || BOARD_NRF54L15DK_NRF54L10_CPUAPP || \
 	BOARD_NRF54L15DK_NRF54L15_CPUAPP