applications: nrf_desktop: Update HF clock lock documentation

Change updates HF clock lock module documentation. Change adds
information about lack of nRF54H SoC Series support, LLPM dependency
and module deprecation.

Jira: NCSDK-29545

Signed-off-by: Marek Pieta <Marek.Pieta@nordicsemi.no>

applications/nrf_desktop/doc/hfclk_lock.rst

@@ -9,7 +9,13 @@ High frequency clock lock hotfix module
 
 Use the high frequency clock lock hotfix module to keep the high frequency clock enabled.
 This reduces the latency before the first packet in a row is transmitted over Bluetooth®, but it also increases the power consumption.
-If this module is disabled, a startup delay of around 1.5 ms will be added to the overall latency of the first packet.
+If this module is disabled, a startup delay of around 1.4 ms (0.85 ms in case of nRF54L Series SoCs) will be added to the overall latency of the first packet.
+
+.. note::
+  The module is deprecated.
+  Use the :ref:`CONFIG_DESKTOP_BLE_LOW_LATENCY_LOCK <config_desktop_app_options>`) Kconfig option instead.
+  Setting the peripheral latency Bluetooth LE connection parameter to ``0`` for a connection that uses Low Latency Packet Mode connection interval on peripheral leads to keeping the high frequency clock enabled.
+  That mitigates the extra HID report latency caused by the high frequency clock startup delay.
 
 Module events
 *************
@@ -24,10 +30,15 @@ Module events
 Configuration
 *************
 
+The module is not supported for nRF54H SoC Series (:kconfig:option:`CONFIG_SOC_SERIES_NRF54HX`).
+
+Make sure that Bluetooth LE Low Latency Packet Mode (LLPM) is enabled in configuration (:kconfig:option:`CONFIG_CAF_BLE_USE_LLPM`).
+Using LLPM connection parameters reduces HID data latency far more significantly than enabling the module.
+
 Enable the module with the :ref:`CONFIG_DESKTOP_HFCLK_LOCK_ENABLE <config_desktop_app_options>` Kconfig option.
 
 Implementation details
 **********************
 
-The high frequency clock is disabled on ``power_down_event`` and reenabled on ``wake_up_event``.
+The high frequency clock is disabled on :c:struct:`power_down_event` and reenabled on :c:struct:`wake_up_event`.
 This is done to reduce the power consumption.