doc: release_notes: Add changes on DFU

Adds the recent changes to DFU to the documentation

Signed-off-by: Jamie McCrae <[email protected]>

Author: nordicjm

doc/nrf-bm/release_notes/release_notes_changelog.rst

@@ -32,12 +32,18 @@ No changes since the latest nRF Connect SDK Bare Metal release.
 Boards
 ======
 
-No changes since the latest nRF Connect SDK Bare Metal release.
+* MCUboot partition size has been reduced from 36 KiB to 31 KiB for the following board targets:
+
+  * `bm_nrf54l15dk/nrf54l05/cpuapp/s115_softdevice/mcuboot`
+  * `bm_nrf54l15dk/nrf54l10/cpuapp/s115_softdevice/mcuboot`
+  * `bm_nrf54l15dk/nrf54l15/cpuapp/s115_softdevice/mcuboot`
 
 DFU
 ===
 
-No changes since the latest nRF Connect SDK Bare Metal release.
+* Support for KMU usage for MCUboot keys has been added, along with west auto-provisioning support (`west flash --erase` or `west flash --recover` must be used during first programming of a board to program the KMU with the keys).
+  This feature can be controlled with sysbuild Kconfig options :kconfig:option:`SB_CONFIG_BM_BOOTLOADER_MCUBOOT_SIGNATURE_USING_KMU` to use KMU for key storage and :kconfig:option:`SB_CONFIG_BM_BOOTLOADER_MCUBOOT_GENERATE_DEFAULT_KMU_KEYFILE` to auto-provision the KMU when using the above west flash commands.
+* The code for the UART MCUmgr application has now been refactored into a separate library to facilitate reuse in other applications.
 
 Logging
 =======